Supporters of this book will all insist that it should be used in conjunction with a course, and this is true, because you can't do hypnotherapy from a page. However, it should also be pointed out that hypnobirth courses are expensive, to the tune of several hundred pounds. This is a business as much as a book. You can use a similar method with Natal Hypnotherapy for much less money.
As to the book itself - well, be a little wary. Some of it is basic common sense: the more fearful you are, the more intensely you will experience pain. Breathing and visualisation can relax you. This is all perfectly true and reasonable.
Some of it is rather affected by the idea of other cultures being 'Noble Savages' - it doesn't use that phrase, but it's very starry-eyed about how other cultures don't use pain relief as if that's always good for the woman, which is just not the case: some women in cultures without medical pain relief have a terrible time. It's also rather judgmental about using pain relief, which is not good news if your birth turns out to be difficult, because generally speaking women who used pain relief are women who found the pain unbearable and will be feeling emotionally fragile as it is.
An important fact can be seen in the opening chapters: the author found that with relaxation, she was able to bear her own children with little pain and distress. Okay, so that speaks to the value of her method, but it also speaks to the fact that she found childbirth comparatively easy: she didn't have to deal with a labour that went on for days, or had the baby in the wrong position, find her labour stalled, or generally speaking had problems that would make things more painful. Reading the book, I got the feeling that she didn't quite grasp that this was not everyone's experience - or possibly that she blamed all labour complications on doctors or bad attitudes and forgot that before medical technology was advanced, death in childbirth was very common, good attitude or not.
She also talks of how in her first two births, doctors intervened at the last minute and imposed on her pain relief that she didn't want or need. This is very bad, but again, I got the feeling that she didn't quite grasp that pain relief isn't an intrusion forced on every woman by doctors who don't understand her. Forcing pain relief on a woman who doesn't want it is cruel, but so is denying pain relief to a woman who needs it, and this book edges towards that cruelty by implying that pain relief is a sign of being brainwashed by doctors. There's a hostility to medicine here that is not in the interests of the many women who will find that medical intervention is something they turn out to need after all.
If it works for you, you'll feel extremely excited about it and praise it to the skies. But it isn't going to work for everyone, the courses are excessively expensive, the author's understanding of other cultures is at times sentimental and patronising, and if it doesn't work for you you'll probably end up feeling worse for having read a book that so explicitly links the pain of childbirth with a bad attitude - it'll make it easier to believe that your suffering was your own fault.
In general, it's a book that's going to get either loved or hated, depending on the birth experience, so shop around for cheaper options and bear in mind that the praising voices are only one side of the story, is my advice.