I liked both Small Angry Planet and Closed and Common Orbit for different reasons. It may have helped that I read them in reverse order; the first book was self-published and sometimes it shows, but by the time I was reading it I was already invested in the universe.

One thing I really, really like about both of them is that this is not a human-centric universe. Humans aren't even all that politically powerful, and it's really interesting to read about a society where we don't run things. I blame John Campbell for a lot of the lingering tendency to center humans (whether Earth humans or not) in much of the better-known SF that includes aliens. Campbell had some very strong prejudices, of which "Earth and humans are Speshul!" was one of the strongest, and his influence marked generations of SF authors.