A Gift from Earth
Author: Larry Niven
 
Only the plateau is habitable. Only the powerful survive . . .
A solitary mountain rises from the searing, toxic blackness of the planet.
Forty mile below, the atmosphere is sixty times as thick as Earth's, and hot enough to melt lead.
The organ banks are the centre of this world. To them the subservient colonists contribute living limbs. And from them the overlords obtain the vital parts that keep them all alive . . . 
 
FUTURA/ORBIT BOOKS 1978 REPRINT
ISBN: 0708880126