The Word for World is Forest by Ursula Le Guin
A group of hominoids called Terrans have completely tapped all the resources on their own planet. To remedy their situation, they are colonizing other planets in their solar system.
The planet they go to in this story is already inhabited by small intelligent primates called Athsheans. The Athsheans live in harmony with each other and with nature, and have a long-standing tradition of non-violence.
However, the Terrans are taking them as slaves, abusing them, taking advantage of their obliging nature, and destroying the forests that are their home. In order to survive, they must rise up and fight the Terrans. But once they have tasted violence, how do they get it out of their system?
When I picked this up, I had just recently began reading science fiction. I am a huge fan of fantasy so this sort of seemed like another step in the same direction. Ursula Le Guin is a fantastic writer. She makes the scenes very vivid in your imagination while still leaving many aspects of the story mysterious.
Not only so, but her novels always have philosophical elements that probe deep and important questions about humanity. Out of the five books of hers that I have read, this one is not my favourite, but it was still pretty good.
Over all, it was a good read. I would recommend it.