"Books of Hours constitute one of the most significant groups of cultural artifacts from the late Middle Ages and Renaissance. Indeed, from the mid-thirteenth to the mid-sixteenth century, more Books of Hours were produced, both by hand and by press, than any other type of book. They were the bestsellers of an era that lasted 300 years. In an era when some of the most important painting was in books, the illuminated miniatures in manuscript Books of Hours are the picture galleries of the Middle Ages. And straddling the revolution of manuscript to print, Books of Hours are the great constant in a sea of changing readership and competing markets" (Wieck, Painted Prayers, The Book of Hours in Medieval and Renaissance Art ).