The absolute best in its field, Wisdom of Yoga is no 'Idiot's Guide to Yoga'; you actually need gray matter in order to read it. However it's well worth it. I don't know of a more enriching, comprehensive (and above all) enjoyable read that will take you to the heart of the YogaSutras and the real purpose for taking up yoga.
I am a clinical psychologist, and, although I have little indepth understanding of yoga philosophy, I found in this book a compelling (and, I believe, accurate) description of the possibilities of juman maturation and development. Stephen Cope's description of the origins and fate of the ego ideal and ideal ego are especially helpful. In this new book, Mr. Cope makes many interesting connections between the psychoogy of th4e contemplative traditions (both yoga and Buddhism) and Western psychological thinking. He makes a good case for the application of these insights to daily life. In addition to the fascinating content, the book is well written; it is a rare delight to find well-crafted prose in a book such as this.