An erudite and popular librarian, Charles Edward Sayle (1864-1924) devoted his career to cataloguing and editing rare books in the University of Cambridge. His obituary praised him as 'a fine example of the type of man who likes to catalogue things in the right order'. This catalogue of incunabula and early printed books (up to 1640) in the University Library was his most important project. Commissioned by the Library Syndicate in 1894, the catalogue was published in four volumes between 1900 and 1907. Even upon completion, Sayle's list was not final, as the rare book collections at the Library were undergoing a period of great expansion, having grown by a third during his cataloguing work, both through purchases and by donations or bequests. It remains, however, a monument of early twentieth-century bibliographical scholarship, and a valuable resource for researchers working on early English books and printing history.