This is the kind of book you can point to when some sneering “literary writing only” nitwit tries to tell you that genre fiction can’t address larger themes or important messages.
In this book, the planet of New Tahiti (as the Earth human refer to it) already has an indigenous population of humans that happen to be short of stature and covered with green fur (I haven’t read a LeGuin book in a while – there is a set universe, but I can’t remember how the various worlds of humans are related). They view the Earth colonists as humans like them, but the Earth colonists don’t share that view, and when they basically enslave the local population and start raping their women, well, you can imagine what happens. They may have been a peaceful people before, but anyone can learn to kill when pushed to their breaking point.
At its heart, this is a story about humanity, and relating to people that are different than you. I didn’t read it because of what’s been happening recently in Ferguson, MO, but it definitely made me think about that more. That’s what good genre fiction will do – make you see the world around you in a different light, and maybe help you frame up difficult issues in a way you hadn’t thought of before.