Hi Archer1, I gotta say I agree with Fools_fool about the Duquete book. People do rave about how accessible it makes the deck but, for me, it was the least inspirational of the ones I have looked at. Still useful though, especially if a beginner.
I find the Book of Thoth a bit dry and not an easy read. I tend to dip into it for specific cards, but as I am not well versed in the theories being discussed some of it is a bit over my head. I used Thoth for many years without a Thoth-specific text book, but the first one I found was called 'Tarot, Mirror of the Soul' by Gerd Ziegler. It basically has descriptions and a few keywords for each card and has explanantions for some of the symbolism. Gerd has a wonderfully inspirational way of describing the energy of each card, and it really opened my eyes to the variety of interpretational styles possible. Ziegler also includes 'indications' for each card, 'questions' which each card poses, and also 'affirmations' to draw empowerment from each card. I personally think this is a cracking book to begin your journey.
If you are looking for a more structured approach, then I did buy the 'keywords for the Crowley Thoth' by Banzhaf & Theler, and this gives a very regimental breakdown of the symbolism of each card and roughly what it means, plus it runs through how this card might apply in terms of profession, relationships, consciousness, weaknesses, strengths, etc also how you might interpret it as a daily card and so on... It is not the most exciting book, but very useful all the same.
As you use your cards, the most important resource will be your own reactions to the deck, but as a place to start then I would suggests Ziegler and the keywords.
Hope this helps
Fury x