Juxtaposition

Stile is a small, quick-witted amateur who has spent two books living a double life -- a lowly serf on the tightly ruled game-world of Proton, and an Adept of magic on its mirror-world twin, Phaze. The barrier between the two realities that let him move between them is now failing, and the forces threatening to erase it are closing in faster than he can master either world's rules. He must find a way to hold two impossible lives together before the choice is made for him. The third novel in Piers Anthony's Apprentice Adept series, following Split Infinity and Blue Adept.