I have been practicing taiji quan since 1986 and was lucky to have come across this book early in my study. Master Jou's book is one of the best on the art, philosophy, and practice of taiji quan. First published in the early 1980s, it was one of the first comprehensive books on taiji with chapters on 1) Roots, 2) Philosophy, 3) Foundation, 4) Classics, 5) Experiences, and 6) Push Hands, the last which is the two-person applications practice in taiji.
Although it has position drawings and explanations for all three of the main taiji styles - Chen, Yang, and Wu -the better part of the book is on the background history and philosophy of the taiji art in the context of Chinese culture. I found the the chapter on Foundation that introduces important parallel practices such as taiji qigong (Tai-Chi Chi-Kung), taiji meditation, and the Chen-style practice of silk-reeling to be exceptionally helpful. The sections on Daoist five-element theory, yin-yang theory, and the Yi-Ching (I-Ching) are excellent introductions to this essential knowledge of the taiji art.
All in all this is an excellent companion for anyone who's pursuing a committed study of taiji. It's no substitute for a teacher however, but once you've found a teacher, this is one of the best books to ground your knowledge of taiji.