A Feast Unknown — Philip Jose Farmer

Sci-fi meets the grittiest of horror and pulp fiction in Grand Master Philip José Farmer's controversial novel set in the Wold Newton universe
 
The legendary Apeman, Lord of the Jungle and bastard son of Jack the Ripper, fights the equally legendary Doc Caliban, Man of Bronze and Champion of Justice. For the loser, it will mean death; for the victor, not just life -- but immortality.
 
Inflamed by strange passions, these titans run amok in an orgy of hate and vengeance, lust and bloodshed. But these two titans have more in common than they could ever have imagined. So who are the dark manipulators of their destiny?