This book presents the 'Chapter on Satan' (Bab al-shaytan) from a long unrecognized Ismaili work called the Kitab al-shajara by the fourth/tenth-century Khurasani dai, Abu Tammam. The satans of Abu Tammam's 'Chapter' are the founders and instigators of the seventy-two heretical sects of Islam. Each sect has been accorded a relatively lengthy description as perceived from a generally Shii and Mutazili point of view. Most entries offer new information about these sects and, in several cases, the account given is for a sect almost completely unknown in the existing Islamic heresiographical literature. The volume contains both a critical edition of the 'Bab al-shaytan' and a complete English translation of it.