The Men in the Jungle — Norman Spinrad

Bart Fraden came looking for a planet to conquer - and found the hell-hole of the galaxy: Sangre - the killer planet. For three centuries Sangre had been dominated by the sadistic Brotherhood of Pain, a priesthood dedicated to torture, slavery and cannibalism. Bart sensed the kind of revolutionary potential that he could manipulate to make himself ultimate ruler. But he hadn't counted on the apathy of a people bred as meat animals and the dreadful power wielded by the Brotherhood. Sangre might cost him more than his life - it might destroy his soul . . .