"If the Holy Bible was printed as an Ace Double," an editor once remarked, "it would be cut down to two 20,000-word halves with the Old Testament retitled as ‘Master of Chaos’ and the New Testament as ‘The Thing With Three Souls.’"

- Charles McGrath, New York Times, May 6, 2007

Ace Double titles are frequently collected, both for their covers and for their affiliation with individual genres. They became known for the dos-a-dos binding format used for many of its early books, although it did not originate the format.

Most of the early titles were published in this "Ace Double" format, and Ace continued to issue books in varied genres, bound dos-a-dos, until 1973. These have proved attractive to book collectors, and some rare titles in mint condition command prices up to $1,000.

A dos-a-dos book has the two titles bound upside-down with respect to each other, so that there are two front covers and the two texts meet in the middle (sometimes with advertising pages in between). This format is generally regarded as an innovation by Ace. It was not, but since Ace published hundreds of titles bound this way over the next 21 years, it became the best-known publisher using the format.

Books by established authors were often bound with those by lesser-known writers, on the premise that this would help new writers gain readers. The main drawback of the "Ace Double" format was that the two books had to fit a fixed page length (usually totalling between 256 and 320 low-height pages). Therefore, one or both novels might be cut or revised to fit. Despite the tag "Complete and Unabridged" on the cover, books so labeled were sometimes still abridged.

Ace Books is the oldest active specialty publisher of science fiction and fantasy books. The company was founded in New York City in 1952 by Aaron A. Wyn, and began as a genre publisher of mysteries and westerns. It soon branched out into other genres, publishing its first science fiction (sf) title in 1953. This was a successful innovation, and within a few years, sf titles outnumbered both mysteries and westerns. Other genres also made an appearance, including nonfiction, gothic novels, media tie-in novelizations, and romances.

Many individual titles are now highly sought after. Much of Philip K. Dick's early work appeared in Ace editions, and is now difficult to find in good condition.

Among the rarest Ace titles are:

• William Burroughs (as William Lee) Junkie (1955, D-015, bound with Maurice Helbrand's Narcotic Agent)
• Harlan Ellison The Deadly Streets (1958, D-312)

The doubles format in itself has proved particularly attractive to collectors, with specialist reference works created for both the mystery and sf books, listing only the doubles. The following codes provide reference to many Ace titles, organized by genre and by format.

• Science fiction: SF Doubles, SF Letter-Series Singles, SF Numeric-Series Singles; (SF)
• Mysteries: Mystery Doubles, Mystery Letter-Series Singles, Mystery Numeric-Series Singles; (MY)
• Westerns: Western Doubles, Western Letter-Series Singles, Western Numeric-Series Singles; (WE)
• Other genres: Doubles, Letter-Series Singles, Numeric-Series Singles; (NA)
• Combined-genre lists: all Ace Doubles volumes; all Ace Singles volumes.
  

The following lists give the individual series titles, for all genres.

D/G/S-series — 599 volumes;
G-series — about 266 volumes;
F-series — about 330 volumes;
M-series — about 66 volumes;
H-series — about 108 volumes;
K-series — about 207 volumes;
A-series — probably 30 volumes;
N-series — 4 volumes;
Numbered series — over 1,000 volumes listed; many more are not included.

Serial numbers

Ace titles have had two main types of serial numbers: letter series, such as "D-31" and "H-77", and numeric, such as "10293" and "15697". The letters were used to indicate a price. The following is a list of series with their date ranges and prices.

D-series — 35¢, 1952 to 1965.
S-series — 25¢, 1954 to 1958.
T-series — 40¢. This series is listed in Tuck's Encyclopedia, but he gives no examples in his index and there are none cited in other bibliographic sources. This series may therefore not exist.
F-series — 40¢, 1960 to 1967.
M-series — 45¢, 1964 to 1966.
G-series — 50¢, 1958 to 1960 (D/S/G series); 1964 to 1968 (later series).
K-series — 50¢, 1959 to 1968.
H-series — 60¢, 1965 or 1966 to 1968.
A-series — 75¢, 1965 to 1968.
N-series — 95¢, 1965 to 1968.

The first series of Ace books began in 1952 with D-01, a western in dos-a-dos format: Keith Vining's Too Hot for Hell backed with Samuel W. Taylor's The Grinning Gismo. That series continued until D-599, Patricia Libby's Winged Victory for Nurse Kerry, but the series also included several G and S serial numbers, depending on the price.

The D and S did not indicate "Double" (i.e., dos-a-dos) or "Single."

There are D-series titles that are not dos-a-dos, although none of the dos-a-dos titles have an S serial number.

Towards the end of this initial series, the F series began (at a new price), and thereafter there were always several different letter series in publication simultaneously. The D and S prefixes did not appear again after the first series, but the G prefix acquired its own series starting with G-501. Hence the eight earlier G-series titles can be considered part of a different series to the G-series proper. All series after the first kept independent numbering systems, starting at 1 or 101.

In January 1969, Ace switched to a numeric coding system. The code depended on the title of the book: specifically, on the first significant word in the title. For example, Tom Purdom's The Barons of Behavior was published by Ace in about 1972 as serial number 04760. The first letter of "Barons" is "B", so the code assigned is fairly early in the numeric range 00000 to 99999.

This procedure for assigning numeric codes was in use at Ace at least into the early 1990s, and may still be in use today. For Ace Doubles, one of the titles was selected and used to determine what serial number would be used. For example, 11560 is the Ace Double The Communipaths by Suzette Haden Elgin, backed with Louis Trimble's The Noblest Experiment in the Galaxy. The serial number here is derived from The Communipaths; a serial number derived from the Trimble would have been about 58000.

For the later numeric series titles, the number is also part of the ISBN. To form the ISBN (if it exists) for one of these books, one prefixes to the serial number a "0" (representing the English language/US), and "441" (Ace's publisher number). The last digit can then be calculated with an ISBN check digit calculator. For example, Christopher Stasheff's Escape Velocity has serial number 21599; the ISBN is 0-441-21599-8.

WHAT FOLLOWS IS A PARTIAL LISTING OF EACH SERIES:

D and S Series
D-001 MY Samuel W. Taylor The Grinning Gismo / Keith Vining Too Hot For Hell (1952)
D-002 WE William Colt MacDonald Bad Man's Return / J. Edward Leithead Bloody Hoofs (1952)
D-003 MY Mel Colton The Big Fix / Kate Clugston Twist the Knife Slowly (A Murderer in the House) (1952)
D-004 WE Lewis B. Patten Massacre at White River / Walter A. Tompkins Rimrock Rider (1952)
D-005 MY Eaton R. Goldthwaite The Scarlet Spade / Harry Whittington Drawn To Evil (1952)
D-006 WE William E. Vance The Branded Lawman / Nelson C. Nye Plunder Valley (1952)
D-007 MY Stephen Ransome I, the Executioner (False Bounty) / Harry Whittington So Dead My Love! (1953)
D-008 WE Allan K. Echols Terror Rides the Range / Tom West Gunsmoke Gold (1953)
D-009 MY Michael Morgan Decoy / Sherwood King If I Die Before I Wake (1953)
D-010 WE Leslie Scott The Brazos Firebrand / Gordon Young Hell on Hoofs (1953)
D-011 MY Day Keene Mrs. Homicide / William L. Stuart Dead Ahead
D-012 WE Dudley Dean Mcgaughty (as Dean Owen) The Man From Boot Hill / Dan J. Stevens Wild Horse Range (1953)
D-013 NA Theodore S. Drachman Cry Plague! / Leslie Edgley The Judas Goat (1953)
D-014 WE Paul Evan Lehman Vultures On Horseback / George Kilrain Maverick With A Star (1953)
D-015 MY William Burroughs (as William Lee) Junkie / Maurice Helbrant Narcotic Agent (1953)
D-016 MY Edmond de Goncourt and J. De Goncourt Germinie'' / Paul Bourget Crime D'Amour (1953)
D-017 MY William Campbell Gault (as Roney Scott) Shakedown / Howard Fast (as Walter Ericson) The Darkness Within
D-018 WE J. Edward Leithead The Lead-Slingers / Samuel Peeples (as Brad Ward) The Hanging Hills (1953)
D-019 MY Hal Braham (as Mel Colton) Never Kill A Cop / Leslie Edgley Fear No More (1953)
D-020 WE Roy Manning The Desparado Code / Allan K. Echols Double-Cross Brand
D-021 MY John N. Makris Nightshade / Lester Dent High Stakes (1953)
D-022 WE Bliss Lomax Maverick Of The Plains / Leslie Scott Badlands Masquerader (1953)
D-023 MY Louis Trimble (as Stuart Brock) Bring Back Her Body / Richard Sale Passing Strange (1953)
D-024 WE Tom West Vulture Valley / John Callahan The Sidewinders (1953)
D-025 NA P. G. Wodehouse Quick Service / The Code Of The Woosters(1953)
D-026 NA Harold Acton and Lee Yi-Hsieh (translators) Love In A Junk And Other Exotic Tales / Charles Pettit The Impotent General (1953)
D-027 MY Bruno Fischer The Fingered Man / Hal Braham (as Mel Colton) Double Take (1953)
D-028 WE Paul Evans Gunsmoke Kingdom / William E. Vance Avenger From Nowhere (1953)
D-029 MY Ross Laurence The Fast Buck / J. F. Hutton Dead Man Friday
D-030 WE George Kilrain South To Santa Fe / Samuel Peeples (as Brad Ward) Johnny Sundance (1953)
D-031 SF A. E. van Vogt The World of Null-A / The Universe Maker (1953)
D-033 MY Carl G. Hodges Murder By The Pack / Frank Kane About Face
D-034 WE Ken Murray Hellion's Hole / Ken Murray Feud In Piney Flats (1953)
D-035 NA Rae Loomis The Marina Street Girls / Jack Houston Open All Night (1953)
D-036 SF Robert E. Howard Conan the Conqueror / Leigh Brackett The Sword of Rhiannon (1953)
D-037 MY Marvin Claire The Drowning Wire / Will Oursler Departure Delayed (1953)
D-038 WE Bliss Lomax Outlaw River / Louis L'Amour (as Jim Mayo) Showdown At Yellow Butte
D-039 WE Frank Gruber Quantrell's Raiders / Frank Gruber Rebel Road (1953)
D-040 MY Cornell Woolrich (as William Irish) Waltz Into Darkness / Malden Grange Bishop Scylla
D-041 MY Day Keene Death House Doll / Thomas B. Dewey Mourning After (1953)

F Series
F-101 NA Joan Sargent Cruise Nurse / Margaret Howe Calling Dr. Merriman (1960)
F-102 MY Bob McKnight The Flying Eye / Clayton Fox Never Forget, Never Forgive (1961)
F-103 WE Harry Whittington A Trap For Sam Dodge / Lee Floren High Thunder (1961)
F-104 SF Kenneth Bulmer No Man's World / Poul Anderson Mayday Orbit (1961)
F-106 WE Brian Garfield Justice At Spanish Flat / Tom West The Gun From Nowhere (1961)
F-107 MY Chester Warwick My Pal, The Killer / John Trinian Scratch A Thief (1961)
F-108 SF G. McDonald Wallis The Light of Lilith / Damon Knight The Sun Saboteurs (1961)
F-110 WE Ray Hogan Track The Man Down / Lee Wells Savage Range (1961)
F-111 MY J. M. Flynn The Girl From Las Vegas / Robert Martin To Have And To Kill (1960)
F-112 NA Jeanne Judson Barbara Ames - Private Secretary / Nell Marr Dean Ratzlaff (as Nell Marr Dean) Fashions For Carol (1961)
F-113 SF Charles L. Fontenay Rebels of The Red Planet / J. T. McIntosh 200 Hundred Years to Christmas (1961)

M Series
M-100 WE John Callahan A Man Named Raglan / Barry Cord Gun Junction (1964)
M-101 SF Leigh Brackett The Secret of Sinharat / People of the Talisman (1964)
M-102 WE Ray Hogan Hoodoo Guns / Rod Patterson Trouble At Hangdog Flats (1964)
M-103 SF Fred Saberhagen The Golden People / Lan Wright Exile From Xanadu (1964)
M-104 WE Tom West Sidewinder Showdown / Dan J. Stevens Land Beyond The Law
M-105 SF Margaret St. Clair Message From the Eocene / Three Worlds of Futury (1964)
M-106 WE Reese Sullivan The Blind Trail / Tim Kelly Ride Of Fury (1964)
M-107 SF A. Bertram Chandler The Coils of Time / Into The Alternate Universe (1964)
M-108 WE Rod Patterson Gunfire Heritage / Wayne C. Lee Warpath West (1965)
M-109 SF G. C. Edmondson Stranger Than You Think / The Ship That Sailed the Time Stream (1965)
M-110 WE Tom West Bushwack Brand / Merle Constiner Wolf On Horseback (1965)
M-111 SF Edmond Hamilton Fugitive of the Stars / Kenneth Bulmer Land Beyond the Map (1965)
M-112 WE Nelson Nye Rogue's Rendezvous / Gun Feud At Tiedown
M-113 SF Damon Knight Off Center / The Rithian Terror (1965)
M-114 WE Brian Garfield (as Frank Wynne) Lynch Law Canyon / Stephen Payne Stampede On Farway Pass
M-115 SF John Brunner The Repairmen of Cyclops / Enigma From Tantalus (1965)
M-117 SF Bruce W. Ronald Our Man in Space / Jack Sharkey Ultimatum in 2050 A.D. (1965)
M-118 WE Merle Constiner Guns At Q Cross / Tom West The Toughest Town In The Territory (1965)
M-120 WE Nelson Nye Ambush At Yuma's Chimney / John Callahan Ride The Wild Land (1965)
M-121 SF Emil Petaja Alpha Yes, Terra No! / Samuel R. Delany The Ballad of Beta-2 (1965)
M-122 WE Roger G. Spellman Tall For A Texan / William Vance Outlaw Brand (1965)
M-123 SF John Brunner The Altar on Asconel / Ted White Android Avenger (1965)
M-124 WE Stephen Payne Trail Of The Vanishing Ranchers / Tom West Battle At Rattlesnake Pass (1965)
M-125 SF Jack Vance Monsters in Orbit / The World Between and Other Stories (1965)
M-126 WE Harry Whittington Valley Of Savage Men / Ben Elliott Brother Badman (1965)
M-127 SF John Rackham We, The Venusians / Fred Saberhagen The Water of Thought (1965)
M-128 WE Brian Garfield (as Brian Wynne) The Night It Rained Bullets / Reese Sullivan Nemesis Of Circle A (1965)
M-129 SF A. Bertram Chandler The Alternate Martians / A. Bertram Chandler Empress of Outer Space (1965)

G Series
G-501 MY Charlotte Armstrong Lewi (as Charlotte Armstrong) Incident At A Corner / The Unsuspected (1965)
G-503 MY Ursula Curtiss The Face Of The Tiger / The Stairway (1962)
G-506 MY Doris Miles Disney Black Mail / Did She Fall Or Was She Pushed?
G-508 MY Ruth Fenisong The Schemers / But Not Forgotten (1965)
G-509 MY Elisabeth Sanxay Holding The Virgin Huntress / The Innocent Mrs. Duff (1951)
G-511 MY Charlotte Armstrong Lewi (as Charlotte Armstrong) The Chocolate Cobweb / Who's Been Sitting In My Chair? (1965)
G-512 MY Elisabeth S. Holding The Blank Wall / The Girl Who Had To Die (1965)
G-513 MY Charlotte Armstrong Lewi (as Charlotte Armstrong) Then Came Two Women / Catch As Catch Can (1965)
G-518 MY Helen Reilly Follow Me / The Opening Door (1965)
G-519 MY Elisabeth Sanxay Holding The Old Battle Axe / The Obstinate Murderer (1965)
G-521 MY Charlotte Armstrong Lewi (as Charlotte Armstrong) Mischief / The Better To Eat You (1965)
G-523 MY Ursula Curtiss The Forbidden Garden / Hours To Kill (1965)
G-524 MY Elisabeth Sanxay Holding Who's Afraid? / Widow's Mite (1965)
G-525 MY Dana Lyon The Tentacles / Spin The Web Tight (1965)
G-526 MY Charlotte Armstrong Lewi (as Charlotte Armstrong) The Mark Of The Hand / The Dream Walker (1965)

H Series
H-20 SF Kenneth Bulmer The Key to Irunium / Alan Schwartz The Wandering Tellurian (1967)
H-21 SF Jack Vance The Last Castle / Tony Russell Wayman World Of The Sleeper (1967)
H-22 SF Tom Purdom Five Against Arlane / Emil Petaja Lord of the Green Planet (1967)
H-27 SF Juanita Coulson Crisis on Cheiron / E. C. Tubb The Winds of Gath (1967)
H-29 SF Walt Richmond and Leigh Richmond The Lost Millennium / A. Bertram Chandler The Road to the Rim (1967)
H-34 SF Mack Reynolds Computer War / E. C. Tubb Death is a Dream (1967)
H-36 SF Emil Petaja Tramontane / Michael Moorcock The Wrecks Of Time (1967)
H-40 SF E. C. Tubb C.O.D. Mars / John Rackham Alien Sea (1968)
H-48 SF Ellen Wobig The Youth Monopoly / Lan Wright The Pictures Of Pavanne (1968)
H-51 SF John M. Faucette Crown Of Infinity / Emil Petaja The Prism (1968)
H-56 SF Ernest Hill Pity About Earth / R. A. Lafferty Space Chantey (1968)
H-59 SF Philip E. High The Time Mercenaries / Louis Trimble Anthropol (1968)
H-65 SF Mack Reynolds Mercenary From Tomorrow / Kenneth Bulmer The Key to Venudine (1968)
H-70 SF Dean R. Koontz Star Quest / Emil Petaja Doom of the Green Planet (1968)
H-77 SF Juanita Coulson The Singing Stones / E. C. Tubb Derai (1968)
H-85 SF Philip E. High Invader on My Back / Donald A. Wollheim (as David Grinnell) and Lin Carter Destination: Saturn (1968)
H-91 SF Laurence M. Janifer and S.J. Treibich Target Terra / John Rackham The Proxima Project (1968)
H-95 SF Clifford D. Simak So Bright the Vision / Jeff Sutton The Man Who Saw Tomorrow (1968)

 Numbered Series
01685 SF Gordon R. Dickson Alien Art / Arcturus Landing
04612 WE Tom West Bad Blood At Bonita Basin / Tom West Rattlesnake Range (1972)
05595 SF Ken Bulmer Electric Sword Swallowers / John Rackham Beyond Capella (February 1971)
06612 SF Mack Reynolds Blackman's Burden / Border, Breed Nor Birth (August 1972)
06707 SF Brian M. Stableford The Blind Worm / Emil Petaja Seed of the Dreamers (February 1970)
06760 WE C. Hall Thompson The Killing Of Hallie James / Ray Hogan The Bloodrock Valley War (1969)
08560 WE Louis Trimble Siege At High Meadow / Tom West The Buzzard's Nest (1973)
09135 WE Clay Ringold The Hooded Gun / Sam Bowie Canyon War (1969)
10293 SF John Rackham Earthstrings / Ken Bulmer The Chariots of Ra (July 1972)
10665 WE Giles A. Lutz The Challenger / Tom West The Phantom Pistoleer (1960)
11182 SF Ron Goulart Clockwork Pirates / Ghost Breaker (March 1971)
11451 SF A. Bertram Chandler Coils of Time / Into The Alternate Universe (November 1972)
11530 WE Louis Trimble The Lonesome Mountains / Dwight Bennett Newton (as Clement Hardin) Colt Wages (1970)
11555 SF A. Bertram Chandler The Commodore at Sea / Spartan Planet
11556 SF A. Bertram Chandler The Commodore at Sea / Spartan Planet (same cover as 11555-1)
11560 SF Suzette Haden Elgin The Communipaths / Louis Trimble The Noblest Experiment (October 1970)
11650 SF Mack Reynolds Computer War / Code Duello (February 1973)
11705 SF Robert Silverberg Conquerors From the Darkness / Master of Life and Death
11738 WE Dan J. Stevens Hunter's Moon / Tom West Corral This Killer (1973)
11785 WE Phillip Ketchum The Cougar Basin War / Louis Trimble Trouble Valley
12140 SF Brian M. Stableford Cradle of the Sea / Ken Bulmer The Wizards of Senchuria (August 1969)
13783 SF A. Bertram Chandler The Dark Dimensions / Alternate Orbits (May 1971)
13793 SF Dean R. Koontz Soft Come the Dragons / Dark of the Woods (November 1970)
13805 SF John Rackham Dark Planet / Nick Kamin The Herod Men (June 1971)
14193 WE Nelson Nye Death Valley Slim /The Kid From Lincoln County
14195 WE Kyle Hollingshead Ransome's Debt / Merle Constiner Death Waits At Dakins Station (1970)
14250 SF Mack Reynolds Depression Or Bust / Dawnman Planet (October 1973)
14265 WE Norman Daniels The Plunderers / Tom West Desperado Doublecross (1970)
15697 SF Philip K. Dick The Unteleported Man / Dr. Futurity (September 1972)
15890 SF A. Bertram Chandler The Rim of Space / Marion Zimmer Bradley The Door Through Space (February 1972)
16640 SF Jack Vance The Dragon Masters / 5 Gold Bands (April 1972)
16641 SF Jack Vance The Dragon Masters / The Last Castle (April 1973)
17000 WE Reese Sullivan The Deadly Deputy / Dan J. Stevens The Dry Fork Incident (1969)
17235 WE Don P. Jenison South To New Range / Clay Ringold Duel In Lagrima Valley (1970)
20571 SF Samuel R. Delany The Ballad of Beta-2 / Empire Star (November 1973)
22576 SF Marion Zimmer Bradley Falcons of Narabedla / The Dark Intruder & Other Stories (December 1972)
22600 SF Dean R. Koontz The Fall Of The Dream Machine / Kenneth Bulmer The Star Venturers (January 1969)
23140 SF Dean R. Koontz Fear That Man / E. C. Tubb Toyman (May 1969)
23775 SF Barry N. Malzberg (as K.M. O'Donnell) Final War and Other Fantasies / John Rackham Treasure of Tau Ceti October 1969)
24035 SF Mack Reynolds The Five Way Secret Agent / Mercenary from Tomorrow (December 1973)
24100 SF John Rackham Flower of Doradi / Jeremy Strike A Promising Planet (May 1970)
24890 SF H. Beam Piper Four-Day Planet / Lone Star Planet
24892 SF H. Beam Piper Four-Day Planet / H. Beam Piper and John J. McGuire Lone Star Planet
24925 WE Merle Constiner The Fourth Gunman / Tom West Slick On The Draw
27235 SF Walt Richmond and Leigh Richmond Gallaghers Glacier / Positive Charge (April 1970)
27251 WE Barry Cord Gallows Ghost / The Long Wire (1967)
27376 WE Tom West Gallows Gulch / The Man At Rope's End (1964)
27400 SF Neal Barrett, Jr. The Gates of Time / Barry N. Malzberg (as K.M. O'Donnell) Dwellers of the Deep (December 1970)
27415 SF Barry N. Malzberg (as K.M. O'Donnell) Gather in the Hall of Planets / In the Pocket and Other S-F Stories (September 1971)
30300 SF Fritz Leiber The Green Millennium / Night Monsters (March 1969)
30701 WE Nelson Nye Rogue's Rendezvous / Gun Feud At Tiedown (1965)
30850 WE Tom West Black Buzzards Of Bueno / Ben Smith The Guns Of Sonora (1969)
31739 WE Edwin Booth Hardesty / Reese Sullivan The Stranger (1972)
31755 SF A. Bertram Chandler The Hard Way Up / Robert Lory The Veiled World (October 1972)
32718 WE Barry Cord Hell In Paradise Valley / Clay Ringold The Night Hell's Corners Died
33460 WE Louis Trimble Wild Horse Range / William O. Turner The High Hander (1963)
33710 SF Neal Barrett Jr. Highwood / Barrington Bayley Annihilation Factor (January 1972)
37062 SF A. Bertram Chandler The Inheritors / The Gateway to Never (June 1972)
37063 SF A. Bertram Chandler The Inheritors / The Gateway to Never
37064 SF A. Bertram Chandler The Inheritors / The Gateway to Never
37108 SF A. Bertram Chandler Into the Alternate Universe / Contraband From Otherspace
37109 SF A. Bertram Chandler Into the Alternate Universe / Contraband From Otherspace
37130 SF Robert Silverberg Invaders From Earth / To Worlds Beyond
37250 SF Marion Zimmer Bradley The Brass Dragon / John Rackham Ipomoea (April 1969)
37365 SF Robert E. Howard The Iron Man / The Adventures of Dennis Dorgan
38500 WE Kyle Hollingshead Ransome's Move / L. L. Foreman Jemez Brand (1971)
42800 SF E. C. Tubb Kalin/ Alex Dain The Bane of Kanthos (September 1969)
42900 SF Lin Carter Tower Of The Medusa / George H. Smith Kar Kaballa (November 1969)
47200 WE L. L. Foreman Last Stand Mesa / Phillip Ketchum Mad Morgan's Hoard (1969)
48245 SF John T. Phillifent Life Without Lancelot / William Barton Hunting on Kunderer (August 1973)
48755 WE Tom West Lobo Of Lynx Valley / Louis Trimble The Ragbag Army (1971)
48885 WE Brian Garfield (as Brian Wynne) Gunslick Territory / John Callahan Loner With A Gun (1973)
49252 SF Philip José Farmer Lord of the Trees / The Mad Goblin (May 1970)
49301 WE Lin Searles Saddle In The Wind / Tom West Lost Loot Of Kittycat Ranch (1965)
51375 SF Philip José Farmer The Mad Goblin / Philip José Farmer Lord of the Trees (September 1970)
52035 WE Eric Allen Marshall From Whiskey Smith / Gene Tuttle Imposters In Mesquite
52180 SF Robert Lory A Harvest Of Hoodwinks / Masters Of The Lamp (July 1970)
53415 SF John T. Phillifent Hierarchies / Doris Piserchia Mister Justice (May 1973)
53540 WE William E. Vance The Wolf Slayer / Brian Garfield (as Brian Wynne) Mr. Sixgun (1954)
57140 WE Ray Hogan New Gun For Kingdom City / The Shotgunner
57601 WE Reese Sullivan Nemesis Of Circle A / Brian Garfield (as Brian Wynne) The Night It Rained Bullets (1965)
58601 WE Merle Constiner Two Pistols South Of Deadwood / William Vance No Man's Brand
58880 SF Sam Lundwall Alice's World / No Time For Heroes (January 1971)
60990 WE Reese Sullivan Man On The Run / John Callahan Odds Against The Texan (1971)
65874 SF Robert Sheckley The People Trap / Mindswap
66093 SF Clark Darlton The Stolen Spacefleet / Kurt Mahr Sgt. Robot
66094 SF William Voltz Seeds of Ruin / K. H. Scheer Planet Mechanica
66095 SF Clark Darlton Heritage of the Lizard People / Kurt Mahr Death's Demand
66096 SF Kurt Brand Saboteurs in A-1 / William Voltz The Psycho Duel
66097 SF K. H. Scheer Savior of the Empire / Clark Darlton The Shadows Attack
66098 SF W. W. Shols The Wasp Men Attack / Ernest Vlcek Atlan #1: Spider Desert
66099 SF Kurt Mahr Menace of Atomigeddon / Clark Darlton Atlan #2: Flight from Tarkihl'
66121 SF W. W. Shols Robot Threat: New York / Hans Kneifel Atlan #3: Pale Country Pursuit
66128 SF K. H. Scheer Atlan #4: The Crystal Prince / Clark Darlton Atlan #5: War of the Ghosts
66160 SF Nick Kamin Earthrim / Walt Richmond and Leigh Richmond Phoenix Ship (December 1969)
66525 SF Murray Leinster The Mutant Weapon / Pirates of Zan (October 1971)
66995 SF Mack Reynolds The Rival Rigelians / Planetary Agent X (September 1973)
67021 SF Marion Zimmer BradleyThe Planet Savers / The Sword of Aldones
67025 SF Marion Zimmer BradleyThe Planet Savers / The Sword of Aldones
67026 SF Marion Zimmer BradleyThe Planet Savers / The Sword of Aldones
67027 SF Marion Zimmer BradleyThe Planet Savers / The Sword of Aldones
67580 WE Ray Hogan The Vengeance Gun / L. L. Foreman Powdersmoke Partners (1973)
68310 SF John Glasby Project Jove / Ken Bulmer The Hunters of Jundagai (August 1971)
70350 WE Nelson Nye Hideout Mountain / Rafe (1962)
71082 SF Claudia Nunes and Rhoda Nunes Recoil / E. C. Tubb Lallia (April 1971)
71372 WE Louis Trimble The Hostile Peaks / Tom West Renegade Roundup (1969)
72260 WE Gordon D. Shirreffs Quicktrigger / Rio Desperado
72360 WE John Callahan Ride The Wild Land / Jernigan (1965)
72400 SF A. Bertram Chandler The Rim Gods / Laurence M. Janifer The High Hex (February 1969)
72401 SF A. Bertram Chandler The Dark Dimension / The Rim Gods
72402 SF A. Bertram Chandler The Rim of Space / The Ship From Outside
72403 SF A. Bertram Chandler The Dark Dimension / The Rim Gods (August 1978)
72525 WE Brian Garfield (as Frank Wynne) Call Me Hazard / Dean Owen The Rincon Trap (1966)
73100 SF A. Bertram Chandler The Road to the Rim / The Hard Way Up
73101 SF A. Bertram Chandler The Road to the Rim / The Hard Way Up
73102 SF A. Bertram Chandler The Road to the Rim / The Hard Way Up
73390 SF Avram Davidson The Kar-Chee Reign / Rogue Dragon

This guide was assembled by booksuncommon.  Any errors are mine. For those I apologize.

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