This is possibly the best book ever written on its subject. It gives a clear and uncluttered picture of both Islam and Sufism, stating exactly what the difference between Sufism and orthodox religion is, and also presents a complete genealogy of its most important teachers and communicators from the Prophet Muhammed onwards. Its compatibility with modern philosophy and thinking is discussed without falling into a fundamentalist stance, although many modern sacred cows are given short shrift. The effect of this uncompromising book is profoundly liberating, because the self-transforming consciousness it represents is considered to be accessible to every man that walks the earth, no matter what their background or faith.