We rejoin Breq after she has reluctantly accepted the position of captain. She's been allowed to pick her lieutenants, except for one Anaander Mianaai insisted that she would take along. She has agreed to go to Athoek Station for her own purposes, to find Lieutenant Awn's sister and do what she can for her. There she gets involved in various machinations of local politics.
I enjoyed this book, but I recognize that it's a very different book from Ancillary Justice. In the first book, Breq was operating more or less alone. (She was accompanied by Seivarden, true, but although she used her to her advantage where possible, Seivarden was not an active participant in her plans and was completely unaware of what was going on until the climax of the book.) There were also frequent flashbacks to when Breq was Justice of Toren/all of One Esk instead of just one body. In Ancillary Sword, Breq is part of a military force again, and although she largely does her own thing she's still operating in an official capacity. We get glimpses of her trying to recapture some of what she has lost through communication with her Mercy, but it's only a shadow of what she was used to when she was the ship. I happen to like both, but it's easy to see how somebody could enjoy the first book but not have the second be their thing. If political scheming SF is your thing, this is an excellent example of it.