This charming medieval biography of the 11th century antinomian Sufi Abu Sa‘id ibn Abu’l-Khayr (967-1049 AD) stands out as one of the most unusual and engaging images of a Sufi Shaikh in the history of Islamic mysticism. The ingenuity of the mystical feats attributed to him and his pronounced antinomian character allow him to be portrayed as behaving outrageously and with great panache in the face of the conservative religious establishment. The accumulation of picturesque anecdotes, the direct, almost naive, simplicity of the narrative style with its surprises and subtle humor, the remarkable intimacy and humanity of the Shaikh’s personality justify ranking the Asrar al-Tawhid as a great classic of Sufi literature. In addition, the variety of settings and wide range of circumstantial detail make the book a rich source of medieval Islamic social and cultural history.