Book excerpt: The book traces the rise of the Fatimid dynasty in the 4th century AH/10th century CE, from its origins in Islamic messianism to power in North Africa and Egypt, and a central position of influence throughout the Muslim world. The first part deals with the problem of Fatimid origins, the second with the establishment of the dynasty and its religious and political programme in North Africa, the third with the success of that programme in Egypt. Using the history of the Fatimids and their doctrine to survey the world of the Mediterranean and the Middle East in the 4th/10th century, the book offers a new interpretation of the role of the dynasty in the history of Islam down to the period of the Crusades.