I've looked through Chang's book, and a lot of his stuff is BS. He say Hanon and Czerny exercises are useless, and that the intuitive method will destroy your playing, when that is not at all true. Although some of this techniques have greatly helped me (such as the parallel set exercises: not for tremolos though), he has a very biased, closed-minded approach. Take everything he writes in that book with a grain of salt: if something works for you and he says it's bad, don't try to conform and start doing things you've never done just because he says they're proper. You should use what works for you, even if it's against what he says.
Chang does not explain it very well. I'm still really confused about what he's trying to say that I should do with my hand, arm, fingers, etc. It'd be better if there were video demonstrations of this rather than writing a description of it. It's like IKEA making their instructions without illustrations.
It's more a book about practise technique. In that respect it's very useful indeed.