Tarnsman of Gor

Tarl Cabot, an English professor, is summoned to a world hidden on the far side of the sun from Earth — a habitable counter-Earth called Gor, seeded with transplanted human cultures and quietly ruled by an alien species, the Priest-Kings. Thrown into an unfamiliar warrior culture built around personal honor, city rivalries and airborne cavalry, Cabot must earn his place, and his skill with a blade, among people who owe him nothing. He trains as a tarnsman, a rider of Gor's giant predatory birds, and is drawn into conflicts far larger than himself. The opening volume of John Norman's long-running planetary-romance series.