If you want to learn the "secrets" behind hypnosis, any book from Bandler can be recommended. Frogs into princes, Persuasion engineering, for example.
The best way to learn hypnosis is to got to hypnosis seminar with Bandler (of course, only to my experience). The first day we were hypnotising each other, successfully. Of course, it may be too much for your budget.. But it's wortht it.
I like bandler's aproach because his background is in physics, not in psychology. His approach is engineer-like, which makes things more easily understandable.
