Mindfuck Books

Anyone have any recommendations for books that will fuck with your head for a person that doesn't read all that often?
I read American Psycho, Lolita, A Clockwork Orange, and A Scanner Darkly (Most particularly enjoyed Lolita). Are there any books in that general sense?

Much appreciated.

Everyone suggests it constantly, but House of Leaves is a good one.  It's the only book I ever stopped reading out of fear.