Split Infinity (Apprentice Adept, Bk. 1)
On the technological, decadent world of Proton,someone is trying to destroy Stile,serf and master Gamesmen.His only escape lay through a mysterious "curtain" revealed by a loving robot. Beyond the curtain lay Phaze-a world totally rulled by magis. Stile soon realizes that Phaze is no escape. Someone has already killed his alternate self, and he was due to be the next victim. On Proton, his fate depends on winning the great games. On Phaze, He can survive only by master magic.