The House of Zeor by Jacqueline Lichtenberg
Pocket Books, 1977
Price I paid: 75¢
Earth is divided between Sime and Gen, both offspring of the ancient race of men—and mortal enemies. The Sime cannot control their thirst for the kill; terrified Gen cannot escape the sinuous tentacles whose grip means death.
Hugh Valleroy, crossing into Sime territory in a desperate search for the woman he loves, comes on a brave new experiment—one that could mean the survival of his world!