[gmw]

Kenny, is it still invisible if it's appeared on The Simpsons? (Well, I know that author has, not so sure about the book.)

From "Dune" by Frank Herbert we get: "Manual of Maud'Dib" and "Mud'Dib, Family Commentaries" ... and many more ... by the Princess Irulan.

Back to John Irving for a moment ... I think I'd have to re-read the books and note down the titles as they went past. Vydorscope mentioned recursion, there's a certain amount of that going on in some of Irving's books, with writer characters writing writer characters.

I've just finished re-reading "Hyperion" by Dan Simmons, and that presents another interesting case. Internally it speaks of the "Hyperion Cantos" by Martin Silenus, but then Simmons' series also gets called the "Hyperion Cantos", and it's all influenced by the real, but incomplete, "Hyperion" poem by John Keats. It gets difficult to extract the visible from the invisible. (ETA: It does have a real invisible book - did I just say that? - "The Dying Earth" by Martin Silenus.)