Psalters—books of the Old Testament Psalms, usually decorated and illustrated—were common in the Middle Ages. They were intended for the private use of a family; a wealthy family, since the production of an illuminated psalter—although they were small, often the size of a modern paperback book—was expensive and time-consuming. Although they were prized possessions when they were made, we can understand if a book in Latin lost the interest of a family over the centuries.
The Macclesfield Psalter is 252 small pages of densely illustrated text. The artist showed a gift for blending the mundane with the absurd. Animals act as humans; humans and animals interact in impossible ways. It also showed more traditional images of holy figures, like Christ appearing on a rainbow, seen yesterday.
Amazon; there are second-hand copies floating around as well.