Unto Zeor, Forever (Sime/Gen, Book 2)

Perhaps the strongest of the Sim/Gen series, which had a strong following during the 70's. Fans of the Vampire filled with angst over the nature of his existance will love this. The series is set in the unspecified future when the human race has split into two species, the Sim who require a monthly feeding of the Energy produced by the Gen. Children are born neither, and at the onset of puberty, become one or the other. When the series opens the Sim and Gen are split into separate nations, with the Sim killing the Gen when they take their energy. However the population will be domed to extinction, unless a way can be found to take the energy required by the Sim from the Gen without harming them. This installment deals with the struggles of the house of Zeor to establish trust between the Sim and Gen and try to spread their solution of a Channel - a special Sim who can energy from Gens without harming them and then transfer it to other Sims