I'm reading The Robots of Dawn by Isaac Asimov, which is fantastic. He's one of my favourite authors. I just finished his book The Naked Sun, which was brilliant and thought provoking even though it started out slowly and I didn't think I'd like it that much at first.
I'm also reading Cosmic Connection: An Extraterrestrial Perspective, by Carl Sagan. Though it's pretty outdated, it's still interesting.
Oh, and I'm reading a book on Javascript, but that doesn't really count. :P