I read Erich von Däniken's Chariot of the God when I was 8 or 9 and eventually became incandescently angry when I eventually realised it was all made up...
On a more positive note I read Catch 22 when I was about 13 or so and I think that gave me some inkling that the world wasn't really going to make much sense!
The odyssey because it's the basis function for most of western thought (wily male human outsmarts gods, witches, and suitors on a long journey home). The best implementation of the monomyth, imho.
Moby Dick because it's not just a book about whaling, it's a book about world philosophy with crazy tangents.
Fire Upon the Deep because it is the best representation of post-singularity technological implications. Was a big inspiration for me going into machine learning and biology.
On a more positive note I read Catch 22 when I was about 13 or so and I think that gave me some inkling that the world wasn't really going to make much sense!