Let's say you've got 3 books on mysticism --

with titles spelled 3 different ways:  

Kabbalah --- Cabala --- Qabbalah

Are they all the same thing? 

Should they be listed in the same categories? 

Or what???

Kabbalah (the most commonly accepted spelling) is a Hebrew word meaning "that which has been received."   It was originally a form of Jewish mysticism -- and among Jews it still is -- but has also been adopted by other groups.  Hence  the differences in spelling.  Because Hebrew is written with a different alphabet, each group made its own decisions about how to render the word into the Roman alphabet.

Although it is not a hard-and-fast rule, the three spellings indicate three very different markets -- and often give a clue as to which group would be most interested in the book.  And that, in turn, gives you a better idea how to list it.  (The same definitions can help buyers find the type of books they want, too.)

Kabbalah is the spelling prefered by writers using the traditional Jewish form of this mysticism.    It is also the spelling used by most Jewish presses.  The Jewish form is monotheistic and is closely entwined with the traditional rituals, liturgy, and practicies of  Judaism.   In some cases, there is also an overlap with Hasidic Judaism, because the Hasidic philosophy incorporates many concepts from Kabbalah.  If you do a search for Kabbalah, you will find primarily Jewish  items.  So, a book of this type would be best listed under:

Books>nonfiction books>Religion, spirituality>Judaism

Cabala is the spelling preferred by what I call the "Christian Cabalists" -- various groups like the Masons, Rosicrucians, Coptics, Gnostics, etc.  During the European Middle Ages, these and other occult groups adopted some of the symbols and imagery of Jewish mysticism, but gave them a Christian theological twist.  For example, they see the Tree of Life as a type of Cross, with Jesus at the center.  They have also mixed in some of the neo-classical mythologies from ancient Greece and Egypt.  While not exactly pagan, the Cabala is not really Jewish, either --  Do a search for Cabala and you will find few, if any, Jewish items, but quite a few occult ones.  So your Cabala book should not be listed under "Judaism."  Instead, try listing it under:

Books>nonfiction books>Religion, spirituality>occult  

Qabbalah (sometimes Qabala or other variants) is the spelling used primarily by neo-pagans, Wiccans, The Golden Dawn, and various other Earth Religions.  (The Q is pronounced like a "K".  It is used to distinguish between two different "K" consonants in the Hebrew alphabet.)  The Qabbalists have adopted some of the symbols of Jewish Kabbalah, most notably the Tree of Life Diagram, but have superimposed various pagan gods and goddesses on the different levels of the Tree.  They also use Tarot Cards, crystal balls, ritual circles, and other magick paraphernalia.  Search for Qabbalah and you find mostly pagan listings.  So a book on Quabbalah should be listed under:

 Books>nonfiction books>religion,spirituality>Witchcraft, Wicca, pagan

As I said above, these categories are not hard and fast.   There can be some overlap, especially among the more eclectic New Age writers.   As a matter of fact, if you want to add a second category to your listing, all three types could be listed under:

Books>nonfiction books>religion,spirituality>New Age 

Some experts in these fields will no doubt disagree with my admittedly simplistic classifications here.  But if you tried the sample searches above, you probably discovered that, for general categorizing on eBay, these three definitions work pretty well.   Use them to better decide where to list your books and, hopefully, get a better price for them!