This study examines the function and use of 15th century religious literature in German as exemplified by two monastery libraries (Tegernsee, Rebdorf). A study of the history of their dissemination reveals the relevance of vernacular texts both for 15th century theology (with special reference to Bernhard von Waging, identified here as translator of St. Bernard of Clairvaux) and for the choice of reading for lay brothers (Konversen). This makes it possible to provide a finer delineation of the >lay library< phenomenon than has hitherto been the case.