I would suggest starting with Lon Milo DuQuette's book first, which will focus on the structure and how to understand the deck and its background. It's absolutely the best place to begin (only place to being IMO).
After that it depends what you're looking for.
Banzhaf's 'The Crowley Tarot' is probably the best if you want reading specific input, but I think maybe is now out of print. Their 'Keywords for the Crowley Tarot' is useful too, but much less detailed.
I think Michael Osiris Snuffin's 'The Thoth Companion' is pretty useful for readings.
If DuQuette's book gets you interested in astrology and/or qabalah some introductory books relating to either would be useful. DuQuette's 'Chicken Qabalah' is quite good, and I like John Frawley's 'The Real Astrology', but you only need a basic understanding of astrology so any introductory text would be fine.
Once you have that under your belt, you could look at Crowley's own book on his Thoth tarot, and/or even an introduction to Thelema (DuQuette's stuff is good again, or his book with Rodney Orpheus if you're interested in the ritual aspects, and also David Shoemaker's work is very approachable). This video series is a good one too (but I'd not start with it
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