This catalogue of Books of Hours, the 'best seller' of the late Middle Ages and Renaissance, presents two dozen Books of Hours mostly dating from the fifteenth and sixteenth centuries. Examples from France, the Netherlands, and Belgium are presented chronologically with illustrations in color for each entry. Highlights include a fine early Dutch Book of Hours with illuminations closely related to those by the artists of the Utrecht History Bibles. There is also a lavish Book of Hours signed with marks by one of the Masters of Otto von Moredrecht; and a high-quality Parisian Book of Hours with an unusual sequence of miniatures by the Master of Jacques de Besancon. Many of these Books are previously entirely unknown and unpublished. An introductory essay explores how illuminated Books of Hours encouraged their readers to picture piety through reading of texts accompanies by visual aid.