Well, I say just fiction because I'm open to it. I enjoy dark / adult fiction such as Bret Easton Ellis, Chuck Palahnuik, Hubert Selby Junior
I enjoy sci fi esque fiction, but not over the top, intergalatic missions kind of stuff. I enjoy work by Vonnegut, Daniel Keyes, H.G Wells, etc.
And finally everything by John Green.
If you like John Green, you should read It's Kind of a Funny Story by Ned Vizzini or The Perks of Being a Wallflower by Stephen Chbosky, assuming you haven't already.