I had seem numerous recommendations and awards for this book, so I could hardly avoid reading it eventually! The protagonist is the last remnant of a large AI, one of hundreds of human avatars associated with a large warship AI, seeking revenge against whoever destroyed the ship and all the other "ancillaries".
I must say, it's rather good. It's not quite to my taste, being the soft end of sci-fi, but it was far more enjoyable than the theoretically-more-my-kind-of-thing Quantum Thief. I guess the thing it reminds me of the most is Scalzi, complete with military setting and all that. The main character is not an immediately sympathetic one, being a shard of a merciless warship in a bloody and ruthless empire. It's a pretty dark world, but our narrator does turn out to be a bit less unpleasant than first imagined.
Different reviewers keep identifying similar features as being of note. Lots of people talk about the approach to gender. Others remark on the portrayal of the lead character as an AI fragment - being both part and a whole simultaneously. Others talk about the way the relationship between the ancillary and Seivarden evolve. I must be the wrong kind of audience, or particularly insensitive to this stuff, because I felt particularly take-it-or-leave-it about all of these, except the business with Seivarden, which I personally thought didn't work.
Despite all that, I still enjoyed it. A minor disappointment compared to my hopes, but I'll be reading the rest of the trilogy as it comes along.