The Doctrine of the Sufis (Kitab al-Ta'arruf Li-Madhhab Ahl Al-Tasawwuf)

The book begins with a discussion of the meaning and proposed derivations of the term Sufi and enumerates names of the great Sufis. It then states the tenets of Islam, as accepted by the Sufis and tries to prove that Sufism as a system lies within and not without the bounds of orthodoxy. Further it discusses the various stations of the Sufis such as fear, hope, love, etc. and also discusses the "technical terms" of the Sufis. The book concludes with descriptions of the various phenomena of Sufism, and of the miraculous dispensations accorded to the Sufis by God.

In fact this is the most valuable and important work on Sufism.