I have the book, and personally I would not recommend it.
There is some good stuff in the book, although I think that it lacks depth in certain areas. The book has 3 key principles that it applies to different parts of the swing i.e. body rotation, wrist hinge, and a constant spine angle. The book basically emphasis a total big muscle swing where the arms are totally passive.
There are 2 main areas where I found that the book lacks. Firstly it talks about the wrist hinge, and having lose wrists, but does not really tell us how the wrists should hinge. Telling the reading that the wrists just hinge naturally does not help in my opinion.
Secondly they state that the downswing is started by turning the hips, straightening the left leg, or pushing of the right leg. I think that this is a recipe to come straight over the top and is exactly what most amateurs struggle with. It does not mention any kind of axis tilt or what should happen to the shoulders as they start down. In my opinion, any book that fails to mention the tilting of the shoulders and sliding of the hips at the start of the downswing is a bad one.
As a side note I have just finished reading "Four Magic Moves to Winning Golf" by Joe Dante. This book has the best description of wrist hinge and starting the downswing I have read anywhere. The book was written in the 60s and is surprising a very "fresh" and easy read.
