It's not just reading the book. "Reading the book" makes you understand the way the brain works and can induce and "help" sustain "real pain" in places you think it to be. He also makes it clear that the advice "it's all in your mind" is just not going to help and only an insult to the sufferer.
If I understand correctly, he does not exclude physical examinations and advises to go through scans to determine anything serious and attend immediately. For the rest, he outlines the process by which, your brain can trick you into "induce real pain" and sustain real pain.
Any kind of relaxation or - a) reading the book = understanding the process b) relaxation/ meditation which takes away your concentration away c) letting out your aggression on some contact sports etc., can help.