Falling Free by Lois McMaster Bujold is about Leo Graf, an engineer sent to teach at a distant space station. What he finds there ends up turning him into an activist.
His students are a genetically modified human subspecies called "quads" who have four arms instead of two arms and two legs. They are also genetically adapted to live better in the low gravity of off world living. While the have the same intelligence, personalities and hopes and desires as humanity, they are treated by the research company as property and nothing more.
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