This volume investigates the historical lineage and biographical details of every individual who has held the office of the papacy. Authors J.N.D. Kelly and Michael J. Walsh provide a comprehensive chronological record, utilizing historical archives and ecclesiastical records to document the lives, tenures, and political contexts of each pope from Saint Peter to the modern era. The text serves as a systematic reference tool for understanding the evolution of the Catholic Church through its leadership.

Experts and historians frequently cite this work as a foundational reference text for academic study of the papacy. Readers often note the scholarly density and the objective, encyclopedic approach maintained throughout the entries.