This book is a pocket-sized slice of Asian wisdom, succinctly covering the history of Chinese internal martial arts, an explanation of chi theory, some basic internal exercises, and a few excerpted "Tai Chi Classics" by revered masters of the art.
Beginners, dabblers, and advanced students could do worse than spend a few bucks on this book; it costs next to nothing, yet it contains genuine, expert advice in a concentrated form. Good stuff.
This is a wonderful summary of Tai Chi Classics by the same author. My Sifu spoke very highly of Waysun Liao as well as Marshall Ho'o, who's works are also available through Amazon. This book, exactly as it's title says, is the essence of the internal martial art of Tai Chi. As a beginner, I have found it a great companion to the physical aspect of the form. If you are serious about the art/philosophy of Tai Chi, then this is a perfect travel version of an even greater book.