Ender's Game (Ender, Book 1), Orson Scott Card; Tor Science Fiction

“A veteran of years of simulated war games, Ender believes he is engaged in one more computer war game when in truth he is commanding the last fleet of Earth against an alien race seeking the complete destruction of Earth.”
Robin’s Note: If you haven’t already read Ender’s Game, it’s a classic for many reasons: a brilliant idea executed in clear but eloquent language.  The idea of using children to fight a war is not unheard of, of course, but Card takes the whole idea and tells if from the point of view of a reluctant child strategist whose brilliance makes him a target for his peers and his enemies.