This book is a distillation of Powers’ 500+ page tome of the same subject, which couldn’t have been an easy task to undertake, let alone accomplish.  More of a history and conceptual introduction rather than a book of teachings, Powers gives a rather broad yet complete overview of Tibetan Buddhism, including a discussion of sectarianism within the tradition as well as the nonsectarian movement.  Powers addresses the differences between each of the sects well while making sure not to neglect the similiarities.  At times the tone seems to favor the nonsectarian movement over Mahayana, so some bias does seem to seep through from time to time, though not to the point of being distracting.  Overall this book does represent a more than adequate overview of Tibetan Buddhism, and is good introductory material for anyone exploring the many paths of the Dharma.  From Snow Lion Publications and available from your local, independent bookstore.