Jacob Mann (1888–1940), a major figure in the fields of medieval Jewish history and rabbinic literature, was an early user of the Cairo Genizah materials to improve our understanding of these fields. This volume, based on papers delivered at a conference at St. John’s College, Cambridge, assesses his scholarly contributions in the light of more recent developments in these areas. Yosef Ofer, Moshe Lavee, and Gila Wachman deal with Mann’s work on the triennial Torah-reading cycle and hafṭarot, synagogue homilies, and a previously unknown midrashic work from the land of Israel. Ruth Langer and Stefan Reif appraise Mann’s liturgical studies. Adiel Breuer, Sacha Stern, and Jennifer Grayson evaluate Mann’s work on halakhic literature, the rabbinic calendar, and the history of the Babylonian yeshivot. Menahem Ben-Sasson reviews Mann’s article on messianic movements during the Crusades. Miriam Frankel and Yoram Erder deal with Mann’s contributions to Karaite studies. Richard Sarason provides an updated biography of Mann and bibliography of his scholarly writings. Together, they portray Mann as a scholar who was captivated by the riches of the Cairo Genizah and devoted his academic career to their exploration and publication.