I am making notes for things I might put in a future exhibition of books illustrated in books, as I happen across them. There are lots of depictions of books in medieval manuscripts, but I think this is the first one I've seen where the book has a tiny but recognizable illustration. (The full IRL page is less than six inches tall.) https://nrs.lib.harvard.edu/urn-3:fhcl.hough:753821?n=2