The Restoration of Sunnism is a study of the early history of Islamic law schools (s. madrasa, pl. madāris) and their professors in late Fāṭimid and Aiyūbid Egypt (495-647/1101-1249). It describes the origin and spread of these institutions, their teachers, and their role in the religious life of Egypt. This work is a revised version of the author's 1976 University of Pennsylvania doctoral dissertation, which remains one of the most important works on the history of the premodern institution of the madrasa to date.

Unlike many publications on the madāris in recent decades, which argue that medieval Islamic legal education was informal and lacked structure, the present work endeavours to detect the elements of structure and order in the institution of the madrasa and in its educational curricula and the practices associated with it. Leiser's ground-breaking work stands out for its attention to detail and to the political, economic, and religious background of twelfth- and thirteenth-century Egypt.