I was the co-author of the book, or at least for most of it. I did not co-author the ancient historical piece with religious references.
This book had the heart and soul of both Hisataka sensei and myself put into it, and it was written over 2 years during my time in Japan. Hisataka-sensei is a brilliant karateka, and the technical information in this book reflects his extraordinary knowledge.
I second the comments of the other reviewer - get the book and read the technical information. Take the preface and the historical perspective and apply your own thoughts. The history of karate is extensively researched, and quite comprehensive.