This book is a comprehensive historical overview of the formative period of Sufism, the major mystical tradition in Islam, from the ninth to the twelfth century CE. Based on a fresh reading of the primary sources and integrating the findings of recent scholarship on the subject, the author presents a unified narrative of Sufism’s historical development within an innovative analytical framework. Karamustafa gives a new account of the emergence of mystical currents in Islam during the ninth century and traces the rapid spread of Iraq-based Sufism to other regions of the Islamic world and its fusion with indigenous mystical movements elsewhere, most notably the Malr cultural context