A novella - or short novel, I'm not sure - by Ursula Le Guin, in classic Le Guin style. (If you notice it listed as part of what looks like a series, it's because the Hainish Cycle books take place in the same universe - but not in a way that makes a reading order very relevant.)
The planet Athshe is a peaceful paradise, covered in lush forests, inhabited by a gentle branch of humanity - because there are humans out there, in the universe, grown from the same genetic material as ourselves, but they haven't necessarily followed the same evolutionary path. When the invaders - colonists - arrive, their call the Athsheans monkeys. Animals. Rats. It's easy, because the Athsheans are so harmless. They don't seem to even understand when they're being tortured - or enslaved.
In order to defend themselves, the Athsheans have to change. The change is forced upon them, and it's not a benign one.
I found it difficult to say much about this book, because the author paints villains with little nuance - it was exhausting to read the constant barrage of the bad guy character's thoughts and actions. That exhaustion wasn't relieved or made worthwhile by the story unfolding around the main characters. I understand what Le Guin is going for, and she does it excellently, I just don't particularly enjoy it. I like my social science fiction with a little more nuance. A little more subtlety, actually. It's uncomfortable to be stabbed in the eye with whatever points are being made, and I don't have much patience for it.
Who should read this book? People looking for a quick example of how science fiction handles "real issues" and not just rockets and lasers. (They would have a wide range of titles by the same author to pick from, though!) Possibly school kids - I'm pretty sure I could have been a huge fan of this if I'd read it when I was in that special "starting to discover people are stupid and mean and racism and sexism are real things help what's going on and where do I point my anger"-phase. Thing is, though I still have all the same buttons, it takes a different kind of story to press them, now. The word for world is forest is not going into my memory as anyone's required reading. (If I wanted to talk about some of the same themes, I might instead mention C.J. Cherryh's Downbelow Station.)