The book offers an in-depth examination of the production, distribution, and use, from the late fifteenth century to the present, of the 74 editions of Books of Hours printed in Italy in the fifteenth century, 198 copies of which have survived. They are today in 82 libraries in 16 countries in Europe and North America. Special attention is paid to the transmission of the texts in print, their stemma editionum, the cycle of illustrations, and the identification of buyers and users, including the question of the price of these first printed copies in comparison to that of contemporary manuscript copies. Viewing this genre from the Middle Ages to the nineteenth century, the study contextualizes the success of these editions over the long term and the phenomenon of the rapid replacement of older incunabula by newer editions. It probes the place of Books of Hours within the first printed provision of liturgical books, the circulation of the Roman Use, the dissemination of the Venetian calendar in Italy and beyond, and looks also at the changes inspired by the Council of Trent. The book includes a complete transcription of all the calendars and 88 plates in colour.