The Invisible Library is a listing of fictional books that are only listed in other books.
Such as: Some More of God's Greatest Mistakes by Oolon Colluphid, courtesy of Douglas Adams' Hitchhiker's Guide to the Galaxy. Or Buttercup's Baby: S. Morgenstern's glorious examination of courage matched against the death of the heart by S. Morganstern, courtesy of William Goldman's The Princess Bride, o'course.
Go. Read. Lose yourself for a time.