Books of Hours
AbeBooks.com currently has an excellent feature about books of hours thanks to our friends at Fine Books & Collections magazine.
As a group, Books of Hours are arguably the most beautiful of all books. They are also some of the most expensive, with modest examples starting in five figures. One of the finest Book of Hours—the richly illuminated Rothschild Prayerbook—sold for a record $13.5 million (£8.6 million) in 1999.
Books of Hours are private devotional books that were enormously popular with wealthy Catholics in the fifteenth century. They were typically structured around the hourly prayers observed in monasteries, and devout Catholics were expected stop eight times a day and recite the appropriate liturgy.