The Earth colony on the planet Loka utilizes genetic engineering to create a caste society.  The lowest of the castes are the GENS, genetically engineered non-humans, born in tanks from a combo of human and animal DNA that gives them special abilities.  The GENS are destined to a life of servitude to the upper classes of trueborns.  Tank sisters Kayla and Mishalla receive their assignments at age 15 and are separated, but both are drawn into secrets, relationships, and mysteries that cause them to question the entire framework of their strict slave-like caste system.  Action and suspense are dispersed in this dystopian science fiction to make this an enticing read with characters that I cared about.  The persistent problems of human nature and our continued inability to evolve into a benevolent species are well portrayed.