Rensime

In the far future, the human race is divided into Sime and Gen, just as it is into male and female. Simes must take energy from Gens each month to live, and in most areas, Simes and Gens live together peaceably. But if the Gen fears when a Sime attacks...then the Gen dies, and the Sime becomes addicted to the kill. Laneff Farris must struggle with her own inner demons as she strives to use science to find a solution to this deadly addiction. An excellent book in a fascinating world.

In the far future a mutation develops and humankind is split into Simes and Gens. Simes "change over" at adolescence into vampire-like creatures that must suction off energy from Gens every month. Ordinarily, this causes the death of the Gen. But then "Channels" are discovered who could safely take energy from Gens and give that energy to Simes. But there are still problems keeping Sime and Gen apart even centuries later. Enter Laneff Farris, whose research may be crucial in the reunification of Sime and Gen. Both Lichtenberg and Lorrah who write books in this series are both good storytellers and create characters to care about. And since each book was written to be read independently, this one can stand alone.