Even as an historian's account of the origins of occult Tarot, this book largely perpetuates Dummett's logically-confused debunking accounts, published in numerous books.
Here're the facts:
1. Tarot was certainly invented in the fourteenth-fifteenth century, in Italy, and was used for a trick-taking game not unlike Hearts, Spades or Bridge (the Trumps were Trumps, you see).
2. In the late eighteenth century, Antoine Court de Gebelin re-invented Tarot as an occult device, as part of his vast project of interpreting everything interesting as Egyptian.
3. Eliphas Levi picked up on Court de Gebelin (we don't know how directly), and through his influence Tarot (as a divination device and later an initiatory and meditational one) became central to the occult revival and now Neopagan and New Age spiritualities.
4. In the nineteenth century, lots of people got interested in Tarot and cartomancy, such that it became a big fad, especially in France.
Now, given all that, Dummett would have us go one step further: since Tarot was not invented for occult purposes, and since Tarot was not handed down since Egypt, Atlantis, or what have you, Tarot as an occult device is stupid and everyone who uses it is an idiot.
Dummett is a distinguished scholar of Frege, if memory serves, and has a top chair in logic, with expertise in epistemology and language. You'd think he wouldn't fall into this elementary logical trap: what makes historical origin (of a word, a practice, an object) necessarily absolutely contiguous with every possible later usage? For example, "occult force" was once (until the late 17th C.) a stock term describing things like gravity, and now it's always and only used to mean magical forces and such; does that mean Dummett's book should be retitled to avoid "occult"? or that Newton was an idiot to call gravity "occult"? It boggles the mind that Dummett can turn off his brain this completely, book after book.
At any rate, in this particular book, rather than going on from this claim to tell us all about how Tarot was (and is) used for playing a card-game (as in other books by Dummett), he and his pals tell us instead about how various interesting characters of the Belle Epoque developed cartomancy into a fad, a craze, and an occult tradition.
Unfortunately, there is no better history of occult Tarot out there, and if you simply discard every editorial or analytical remark, it's not even all that bad. Of course, that's rather a lot to cut.
If you want the history of occult Tarot from about 1790 to about 1900, this is the only place to go. Just disregard everything except factual statements (and consider carefully whether any given remark is really opinion masquerading as fact), and be ready to look things up in the notes if the authors don't make it clear.
Someday somebody will do a Ronald Hutton on Tarot, and things will be better. Until then, Dummett is as good as it gets. Too bad he's so miserable.
Incidentally, if you want the original texts on Tarot, they've been published, in French (try amazon.fr -- American Amazon doesn't have it):
Court de Gebelin, Antoine. _Le Tarot_. Ed. Jean-Marie L'Hote. Paris: Berg, 1983. ISBN 2.900269-30-X.