Through examples from the Zen school, Taoism, the school of esoteric Buddhism and Confucianism, Master Nan presents exercises and meditation techniques to help one attain Tao.
It seems to me that the book tried to present itself somewhat systematically yet is actually quite messy. The structure and examples used do not really help clarify the matter of enlightenment. The cryptic Ch’an verse and poetry is presented with very little interpretation or relevance. Quite like Tao and Longevity, Nan lays out different perspectives and theories without arguing convincingly from any one of them.
I am also sceptical about some of the recommendations. For example, is eating grain and having wet dreams really going to prevent someone from reaching enlightenment? However, some recommendations, like fasting one day a week, probably is good for health.
The best aspect of the book is the author dispelling numerous illusions and misconceptions, such as samadhi not equating to enlightenment, the pitfalls of naturalism (“going with the flow”) and ‘zombie Zen’, warning against any ‘spiritual experiences’ (gong fu), etc. Nan really emphasises the body transformation, though this seems to happen through cessation-and-contemplation meditation, ie letting the chi work naturally, not getting in its way, rather than deliberately trying to cultivate chi and the channels etc. Many spiritual teachers do speak of physical transformations, so this may be true (even science recognises that the brain changes after meditating for a long time).
I reckon that the subsequent book in the series sheds more light on the practice, but I have not read it so I cannot confirm it. Some good information, all in all, but generally I would not recommend.