Apprentice Adept

On the technological, decadent world of Proton, someone was trying to destroy Stile, serf and master Gamesman. His only escape lay through a mysterious “curtain” revealed by a loving robot.
Beyond the curtain lay Phaze—a world totally ruled by magic. There, his first encounter was with an amulet that turned into a demon determined to choke him to death. And there, he soon learned, his alternate self had already been murdered...

In this brilliantly satisfying conclusion to the epic adventure begun in Split Infinity and continued in Blue Adept, Piers Anthony again proves himself a consummate master of both science fiction and fantasy.

Stile had problems—two whole worlds of problems, in fact. 
On Proton, a world of future science, his murder was averted only by the help of a lovely robot, who sent him through an invisible “curtain”...