One of my loves about the Middle Ages is the study of Books of Hours, those personal prayer books from the 13th-16th centuries of which so many lovely examples survive. I've manfully restrained myself from greedily collecting all the handsome facsimile copies in print... except for a few, of course, plus many less extravagant books about them. I just got Painted Prayers by Roger S. Wieck, and was reminded that I haven't looked around the Internet lately to see what was currently out there. (Regrettably, Painted Prayers is out of print, and I had meant to get it but not gotten around to it until this week... I did not pay anything like the prices for used books shown here. Just in time, I guess.)
Here is a link to a Book of Hours owned by Oberlin College, the Artz Hours, all of the pages of which are shown on successive pages. Very interesting.