Harry potter

Also you could try these science fiction novels:
Vacuum Diagrams
Evolution
Ring
Timeships
These are by Stephan Baxter and are all excellent reads, however they are around 600+ pages each and the science involved is pretty complex, but hey at least you'll learn something

If you're library has manga I'd get Death Note, it's about an honors student, Light Yagami, that finds a note book that kills anyone who's name is written into it. It's a suspense, intellectual battle kind of story.
A Wrinkle In Time is a nice easy Sci FI novel but it's still one of my favorite.