Let there be no difference made among you
I've read the Book of Thoth by Crowley on three separate occasions. The first time I read it it made very little sense to me. The second time I read it was years later, after, inspired I would imagine by the energy of the Thoth deck and the Book of Thoth, I managed to accept the Law of Thelema - the paradigm model upon which Crowley's images and attitude towards the cards have been drawn. The third time I read it I was looking to prove a point to myself, a point I am quite willing to prove at any time - and that is that Crowley in no way changed the meanings of the divining use of Tarot when he made certain discoveries and alignment changes to its mystical layout. What he did change was the paradigm from which the interpretations should be viewed. For example, a hotly dealt with card in this topic is Lust. Although Crowley re-adjusted its position for us by placing it as the Eleventh (not the Eighth) Trump and giving it the title he gave it, he still defines its interpretation the same way (in slightly different words though, less he be merely repeating) all other LWBs do. In the Book of Thoth, on page 257 of my copy, he gives this for ATU XI : Courage, strength, energy and action, une grande passion; resort to magick, the use of magical power.
The Book of Thoth (book) is a great book, but don't expect it to be an easy read nor do most find it useful for divination purposes. Study the Qabalah and Astrology and all that you can get your hands on about Tarot. Do not disregard ANY of your previous learning - do not throw the baby out with the bath water. The Book of Thoth (deck) is an excellent tool for divination and meditation.