"I have had lessons with the top coaches in the world and never seen them use or refer to the bible. I find that the best coaches will give whatever technical information they feel the student is ready for,any more than that is distacting and takes their thaughts away from what the teacher is trying to get them to do. It's one thing to understand (?) what the book says and be able to dance it at a high leval. That's why we need good teachers. You can spend a year reading the book and I'll spend it with a top coach."

The problem is that there are many people with impressive world results who give advise inferrior in accuracy
compared to what has been written down.
Get just a round or two removed from the top ranks, and you find people who got where they are based on their abilities as athletes, performers, etc, not on their actual technical accuracy. You need one of the few who not only took a top place, but really understood why, to get better advice. But reading about dancing takes a lot of background knowledge, too and so is definitely not for everyone.