Zephyros,
I thought about this some more. What it all comes down to is that for you and some others here, Thelema is a religion that you seem to subscribe to whole-heartedly. And the BoT and deck naturally are among its holy scriptures.
I wouldn't put it quite like that.
I don't call myself a Thelemite or anything else, actually. If I believe in anything it is in literary contextuality. A Tarot deck with accompanying literature is a work like any other, and I look at in the context of its own rules. In Star Trek, faster than light travel is a normal thing, but it doesn't work if you don't accept that basic premise of suspension of disbelief because the story has the rules of its own universe.
If someone wants to ignore everything Crowley wrote about the deck, that's fine, but it
is their own view and opinion and this should be made clear when writing a book about the deck. In many cases there's no question about what is there and why, and many things that aren't in the Book of Thoth can be found in others of Crowley's works if anyone wishes to find them. The symbolic language is laid out and works as a system where every element is usually built on another. I'm not ragging on Arrien, I did that enough in the thread I linked to, but her book is an example of where that language is set aside. It's like writing a review about a movie you've never seen, or a book you've never read.
Whether or not her ideas have any worth is debatable, but beside the point. I think one should expand their education to include all possible sources about a subject, which is why I read her book in the first place. But it is also important to get one's facts right first, to know what's
really there, and only then to explore other avenues,
especially in a work like this one's who's purpose is to redefine old terms. When different ideas are debated I usually don't interject with "that's not Crowley," and I'm not in a position to defend his legacy, but in a thread such as this one which is basically about study of the Thoth by a beginner I can't recommend general symbolic study or books that say they treat with the deck but are the personal projections of the authors. If you read
The Tarot Handbook you'll get very little about the Thoth, but you
will get to know Angeles Arrien pretty well. Same goes for projecting RWS meanings onto the Thoth, or the other way 'round. The end user can and should develop their ideas, but there's no excuse for misinforming people.
Arrien makes Thothies itch not because she goes against Crowley's grain, but because she doesn't understand the material, and makes it a selling point and something to be proud of. She says as much in the introduction. It would be one thing if she threw the BoT out the window because she didn't agree with it, but she affirms that she found it difficult, so she set it aside. That's fine, not everyone is into the occult, but it takes a special brand of hubris to say that and then write a book about what you admit you don't understand.