The imaginary book that contain all possible books.
I think I saw the idea in GödelEscherBach
and it was inspired by the writings of JorgeLuisBorges.
Most recently, a variant on this idea has been instantiated online at 
http://www.invisiblelibrary.com/ which is also heavily influenced by Borges.
-- VectorKharin
The Crimson Hexagon is a detailed list of the books that Borges never wrote.
-- DavidLucifer
See other InterestingMemes.