The book is a clear, informative and facsinating guide to the development of power in Xing Yi Chuan, although practicioners of other arts (particualy ba-gua and tai chi) will find the exercise contained herein very useful. The photographs are excellent, the best quality I have seen in any martial arts book. The sixteen exercises form a complete set, and described in painstaking detail. As such, they form a very good basis for anyone who wishes to incorporate this kind of training into their practice.
However, the book contains a lot more than this. The first chapter explains much of the lineage of the Xing Yi masters from whom the nei gong exercises were described. The book then details much from the Xing Yi "classics". Having never seen this material before, it made a very insightful read. Next, there is a chapter devoted to stance keeping, with particular reference to san ti shi (a fundamental aspect of Xing Yi practice), before details of the nei gong exercises themselves. Finally, a brief chapter details the use of the long spear in advanced training. There's a lot of information packed into this book, and as such it represents good value for money.
However, there are a few minor criticisms. The book feels a little like a 'mish-mash' of ideas, although it certainly does not lack clarity or depth of explanation. This is really a matter of taste, and does not distract from the overall quality. The first chapter could do with a little refining, as it does go into rather too much depth about all of the Xing Yi practicioners - it sometimes reads like a Chinese telephone directory, with a barrage of names!
Overall, this is an excellent book. The clear method in which the material is presented also dispel any mysticism surrounding the internal martial arts. If you are seeking the ability to catch bullets in your teeth by focussing your chi, you would be advised to look elsewhere.