Ancillary Justice by Ann Leckie
This book got a lot of buzz when it came out. I borrowed a friend's copy recently so I could read it for the Hugos (since Orbit has decided not to put the whole book in the packet, just an excerpt).
In the far-distant future, humanity has spread throughout the galaxy. The Radchaai Empire has expanded for millennia, but the Lord of the Radch has decreed that a particular annexation will be the last.
The narrator, Breq, was present at the final annexation as the starship Justice of Toren and its ancillaries (AIs in human bodies that act as soldiers). She is separated from her ship, and when she stumbles across an old captain of hers, lying face-down in the snow, she cleans her up and drags her along on her quest.
The Radchaai language doesn't have a gendered third person pronoun, so the narrator uses she as the generic term. (Which leads to sentences like "she was probably male.") It's an interesting linguistic trick, which mostly works. Breq has trouble using the right pronouns for people when speaking languages other than Radchaai, which is too Sapir-Whorfian for me to believe. But it's an interesting conceit.
There is a lot of politics going on, which Breq is wrapped up in, of course, and it's different from your standard-issue space opera. (I like standard-issue space opera, but change is always good.) Class issues are discussed front and center several times.
It took a while for me to get into it (Leckie dumps terminology on you and expects you to run with it, which I generally find frustrating), but once it was explained how the narrator could be in multiple places at once and what Esk and Amaat and all that meant, I found it a much easier read. Then I read the hell out of it.
If you like space opera, you should definitely read this book.