[Kris Verdeyen]

Flatland and Contact are both great reccomendations - I second both.

Others that you might want to look at are Hyperspace by Michio Kaku and Godel, Escher, Bach: an Eternal Golden Braid by Douglas Hofsteader. Both of these are non-fiction, so they might lie outside what you're asking for, but they are both fantastic books.

Hyperspace explores some of the same themes as Flatland (in fact, it references Flatland extensively). In the early chapters especially, it explores the concept of extra-dimensional space in art and culture, but it also paints an exciting picture of the newest theoretical physics.

GEB:EGB is the best book most computer science majors have ever read (if you indulge stereotypes). It explores a wide array of topics in mathmatics, Computer science, psychology, art, music, cognitive science, and biology, and links them together so as to give you an amazing viewpoint. After each chapter is a short dialogue that illustrates the previous chapter's subject. The material is pretty advanced, I first started reading it my sophomore year in college, and put it down after I realized I was out of my element. When I picked it back up my senior year, I was amazed. So if you can't "get it" right now, don't let it bug you too much.

And check out The Hot Zone, as well.