Book of Hours
The Book of Hours was a daily guide to devotion. By the mid-15th century these books had become commercially produced items whose sale was directed to the carriage trade. They were not typical manuscript books, and would have furnished printers a model impossible to emulate.
Digital full versions of this beautifully crafted 15th-century illuminated manuscript and other medieval manuscripts are available at Lehigh University Libraries' Digital Library of Illuminated Manuscript Project: