“The Invisible Library is a collection of books that only appear in other books. Within the library’s catalog you will find imaginary books, pseudobiblia, artifictions, fabled tomes, libris phantastica, and all manner of books unwritten, unread, unpublished, and unfound.”

I’ve only looked through a few titles, but my favorite so far: De pelendis mascarendisque cardinalium mulis (or as they translate it, How to Beat the Shit out of a Cardinal’s Mules). It’s worth visiting the site just to read Rabelais’ entries.