House of Leaves, by Mark Danielewski--I can't really describe it, but it's very weird and it will make you start thinking weird things. It's not horror but it's quite scary.
Palimpsest, by Catherynne Valente--sexually transmitted cities. Nuff said.
The Well of Lost Plots, Jasper Fforde--sci-fi mystery fantasy literary novel, where novel characters escape from their own books and plot devices are for sale, cheap.
If On A Winter's Night A Traveler, Italo Calvino--it's a book about reading a book called If On A Winter's Night A Traveler, which is a book about reading a book called If On A Winter's Night A Traveler, which is a book about...
Appleseed, by John Clute--this is space opera very well disguised as something crazy
The Big U, Neal Stephenson--basically a huge battle within a university, RP nerds versus cheerleaders vs faculty vs giant radioactive rats