These books are currently be published by Grosset and Dunlap and are hardbacks. Book numbers 1 to 38 have been rewritten since they were first published. The first versions before they were written over again are usually called the "originals." Here is how I classify how good I thought the book was.
A+ Extremely good, way above average: Best possible rating.
A Extremely good, way above average.
A- Extremely good, way above average.
B+ Above Average
B Above Average
B- Above Average
C+ Average
C Average
C- Average
D+ Below Average
D Below Average
D- Below Average
F- Not worth reading unless you want to read the books in order. Not many books will be an "F."
Note- I have not read every original or book on this list.
Remember, just because I don't like a certain book doesn't mean someone else couldn't like it.

1. The Tower Treasure C Original Version: Too similar to read both.
   
2. The House on the Cliff A- Original Version: Too similar to read both.
3. The Secret of the Old Mill C Original Version B Note; this is the book in which Frank and Joe get their motor boat, The Sleuth.
   
4. The Missing Chums C Original Version A
5. Hunting For Hidden Gold B Original Version B
6. The Shore Road Mystery C Original Version B
   
7. The Secret of the Caves D Original Version _
8. The Mystery of Cabin Island B- Original Version: Too similar to read both. Note- This book is a favorite for many Hardy Boys fans.
9. The Great Airport Mystery B- Original B
   
10. What Happened at Midnight A- Original_
11. While the Clock Ticked A- Original: Too similar to read both.
12. Footprints Under the Window F Original C+
13. The Mark on the Door original F
    
14. The Hidden Harbor Mystery C+ Original_
15. The Sinister Signpost C Original A+ This is my favorite Hardy Boys book.
16. A Figure in Hiding C Original C+
17. The Secret Warning B- Original B
    
18. The Twisted Claw B- Original: Too similar to read both.
19. The Disappearing Floor B Original A Note on the original; Much to my surprise, many people consider this book their least favorite Hardy Boys mystery.
20. (The) Mystery of the Flying Express B- Original_ Note- This is the first book in which Frank and Joe can pilot a plane (even though it doesn't say). The original version has "the" in the title.
    
21. The Clue of the Broken Blade C Original Version_
22. The Flickering Torch Mystery B Original B+
    
23. The Melted Coins C Original C+
    
24. The Short-Wave Mystery B+  Original_   Note: All the original versions between 25 and 38 are very similar to the new versions and it is not worth reading both.
    
25. The Secret Panel C+ Note- This book was very mysterious.
    
26. The Phantom Freighter C+ Note- This book was one of the funniest Hardy Boys books.
    
27. The Secret of Skull Mountain B
28. The Sign of the Crooked Arrow B-
    
29. The Secret of the Lost Tunnel C
    
30. The Wailing Siren Mystery A
31. The Secret of Wildcat Swamp B
    
32. The Crisscross Shadow C+
    
33. The Yellow Feather Mystery C
    
34. The Hooded Hawk Mystery D Note- Too much of the book was spent on learning about hawks.
35. The Clue in the Embers C
    
36. The Secret of Pirates' Hill B-
    
37. The Ghost at Skeleton Rock B-
    
38. The Mystery at Devil's Paw (retitled Mystery at Devil's Paw) A Note- This was the last Hardy Boys book that was rewritten from the old version into a new version.
39. The Mystery of the Chinese Junk C Note- The word "junk" is  meant  to mean a Chinese boat, not garbage.
    
40. Mystery of the Desert Giant C+
    
41. The Clue of the Screeching Owl C
    
42. The Viking Symbol Mystery A-
    
43. The Mystery of the Aztec Warrior C
    
44. The Haunted Fort C-
    
45. The Mystery of the Spiral Bridge D+
    
46. The Secret Agent on Flight 101 C+
    
47. Mystery of the Whale Tattoo C
    
48. The Arctic Patrol Mystery C
    
49. The Bombay Boomerang B-
    
50. Danger on Vampire Trail B-
    
51. The Masked Monkey C
    
52. The Shattered Helmet C
    
53. The Clue of the Hissing Serpent C
    
54. The Mysterious Caravan C+
    
55. The Witchmaster's Key B-
    
56. The Jungle Pyramid B
    
57. The Firebird Rocket B+
    
58. The Sting of the Scorpion C+                                                                                                                                                                                     The Original hardbcover series published by Grosset and Dunlap is complete. Now, the rest of the series is in paperback starting with #59 and going on until #190 when the series ended. In 1979, the first "Digest" hardy boys book, as they were called, was published by Wanderer a publishing company. Wanderer published numbers 59 to 85. Uncommon hardcover versions of the Wanderer books can be found. Eventually, Minstrel began printing the paperbacks and reprinted all the books printed by Wanderer without the the illustrations inside the book and with new cover art. Also, starting in 2005, Grosset and Dunlap began printing  #'s  59-66  which had been out of print since the 1990's. These Grosset and Dunlap books included the Wanderer cover art and internal pictures.
    
59. Night of the Werewolf B+
    
60. Mystery of the Samurai Sword C Note: I would recommend this book for older Hardy Boys readers only. It is more complicated.
61. The Pentagon Spy A-
    
62. The Apeman's Secret D-
    
63. The Mummy Case B
    
64. Mystery of Smugglers Cove A+ Note- Great Book!
65. The Stone Idol C+ When Frank and Joe travel to Antarctica in this book, they have now traveled to all seven continents.
    
66. The Vanishing Thieves C  The Vanishing Thieves is the last book being published by Grosset and Dunlap currently (although at the end, it says the next book is The Outlaw's Silver. All the books after this are out of print except a few books numbered in the high 100's, published by Simon and Schuster.
67. The Outlaw's Silver B-
    
68. The Submarine Caper (retitled Deadly Chase) F Note- not only was there not much action until the end, but the book was confusing to read. There were at least four people with the first name of Herr, more were mention, and all the names were German. Instead of having Fenton with them, they worked with a German detective called Gerhard. Frank and Joe were the only reappearing characters from other books. It's a no wonder they had to change the title of the book because it is so boring. Recommended only for devoted Hardy Boys fans who want to read the books in order.
69. The Four-Headed Dragon B Note- There are no dragons in this book but it is still good.
70. The Infinity Clue C+
    
71. Track of the Zombie C
    
72. The Voodoo Plot C
    
73. The Billion Dollar Ransom A- Who is worth a Billion dollars? Great book!
    
74. Tic-Tac-Terror D+
    
75. Trapped at Sea B
    
76. Game Plan for Disaster D+
    
77. The Crimson Flame C-
    
78. Cave-In (retitled Cave-In!) A Note- This book was written in the style of the original versions of #1-38.
79. Sky Sabotage C-
    
80. The Roaring River Mystery B
    
81. The Demon's Den B Note- Some science in this one.
82. The Blackwing Puzzle B+ This is the last Hardy Boys book with internal illustrations. It is also the last book with the original Wanderer cover style.
83. The Swamp Monster C+ This new Wanderer cover style was used just for this book. This is, in my opinion, the last Hardy Boys book with the same writing style as numbers 1 through 82. I will make an attempt to explain the future styles of writing further in the guide.
84. Revenge of the Desert Phantom C+ Note- This book and #85 (The Skyfire Puzzle) are more like Casefiles Hardy Boys books because they are more violent. I was glad this style of writing only lasted two books not because of the violence but because of the difference between regular Hardy Boys books. Another boy was trying to date Iola Morton. The Hardy's were firing bullets from a tank. It did not make a good Hardy Boys book. Why the C+? I tried to average it with #85, not with the rest of the series. The new cover style is almost identical to the Minstrel cover art style and is used up until #135. This was originally printed by Wanderer. The average page numbers per book decreases from about 180-190 to about 160 pages.
    
85. The Skyfire Puzzle C Note- Mr. Stone, from Sky Sabotage appears in this book. This is the last Hardy Boys book in this series published by Wanderer.
86. The Mystery of the Silver Star C+ Note- This book is in a new style of Hardy Boys writing. The Hardy Boys really do not have much of a reputation. They are not very good friends with Chief Collig (although they are good friends with Con Riley, a character that had not appeared in many of the digests before this)! I know Con Riley appeared in one of the following books: #86, 87, 88, 89, and/or 90. Phil Cohen is now really interested in computers and stays this way for the rest of the series. There are no Hardback versions of these books, and there probably isn't any in the last five volumes either. The average page length per book decreases down to 150 pages. All books from #86-170 are printed by Minstrel.
87. Program for Destruction B-
    
88. Tricky Business B-
    
89. The Sky Blue Frame B Note- This was a fun Hardy Boys book to read.
90. Danger on the Diamond B-
91. Shield of Fear C- 
92. The Shadow Killers D+
    
93. The Serpent's Tooth Mystery
94. Breakdown In Axeblade
95. Danger On The Air
96. Wipeout
97. Cast of Criminals
98. Spark Of Suspension
99. Dungeon Of Doom
100. The Secret Of The Island Treasure
101. The Money Hunt
102. Terminal Shock
103. The Million-Dollar Nightmare
104. Tricks Of The Trade
105. The Smoke Screen Mystrery
106. Attack Of The Video Villains
107. Panic On Gull Island
108. Fear On Wheels
109. The Prime-Time Crime
110. The Secret Of The Sigma Seven
111. Three-Ring terror
112. The Demolition Mission
113. Radical Moves
114. The Case Of The Countereit Criminals
115. Sabotage At Sports City
116. Rock'N'Roll Renegades
117. The Baseball Card Conspiracy
118. Danger In The Fourth Dimension
119. Trouble At Coyote Canyon
120. The Case of The Cosmic Kidnapping
121. The Mystery In The Old Mine
122. Carnival Of Crime
123. The Robot's Revenge
124. Mystery With A Dangerous Beat
125. Mystery On Manatunk Island
126. Racing To Disaster
127. Reel Thrills
128. Day Of The Dinosaur
129. The Treasure Of Dolphin Bay
130. Sidetracked To Danger
131. Crusade Of The Flaming Sword
132. Maximum Challenge
133. Crime In The Kennel
134. Cross-Country Crime
135. The Hypersonic Secret
136. The Cold Cash Caper
137. High-Speed Showdown
138. The Alsakan Adventure
139. The Search For The Snow Leopard
140. Slam Dunk Sabotage
141. The Desert Thieves
142. Lost In Gator Swamp
143. The Giant Rat Of Sumatra
144. The Secret Of Skeleton Reef
145. Terror At High Tide
146. The Mark Of The Blue Tattoo
147. Trial And Terror
148. The Ice-Cold Case
149. The Chase For The Mystery Twister
150. The Crisscross Crime
151. The Rocky Road To Revenge
152. Danger In The Extreme
153. Eye on Crime
154. The Caribbean Cruise Caper
155. The Hunt For The Four Brothers
156. A Will To Survive
157. The Lure Of The Italian Treasure
158. The London Deception
159. Daredevils
160. A Game Called Chaos
161. Training For Trouble
162. The End Of The Trail
163. The Spy That Never Lies
164. Skin & Bones
165. Crime In The Cards
166. Past And Present Danger
167. Trouble Times Two
168. The Castle Conundrum
169. Ghost Of A Chance
170. Kickoff To Danger
171. The Test Case
172. Trouble In Warp Space
173. Speed Times Five
174. Hide-And-Sneak
175. Trick-Or-Trouble
176. In Plane Sight
177. The Case Of The Psychic's Vision
178. The Mystery Of The Black Rhino
179. Passpart To Danger
180. Typhoon Island
181. Double Jeopardy
182. The Secret Of The Soldier's Gold
183. Warehouse Rumble
184. The Dangerous Transmission
185. Wreck And Roll
186. Hidden Mountian
187. NoWay Out
188. Farming Fear
189. One False Step
190. Motocross Madness Note- Last book in series. Undercover Brothers series is created after this book.
     

To be continued.