Ender's Game by Orson Scott Card is one of my favorite books ever. If you're bothered by sci-fi then you won't like it. If you don't care for sci-fi but are not bothered by it, it might fit you. It's about a gifted child who is a second-class citizen, abused by his psychotic brother, and protected by his sane sister. He gets drafted, struggles through school as an outcast nerd, and winds up in charge, leading the military defending society against the worst attack ever.
http://en.wikipedia.org/wiki/Ender's_Game
