Maybe off-topic oiling, but:
Personally, I found his tip about learning difficult fingering combinations worth the price of the entire book!
There is a section where he mentions tapping the fingering with force to the tonehole, then immediately relaxing it (without blowing). I found that several iterations practicing this way solved a number of difficult passages that I had been battling with for a longer time. So simple yet s effective. Also works on traverso and clarinet of course.