If Ancillary Justice plays like a blockbuster science fiction movie that also happens to be very smart and relevant, Ancillary Sword plays like an episode of the Imperial Radch tv show. Said tv show is also pretty smart and relevant, and it does a solid job of extending the themes of Justice, but it doesn't expand on those themes, and it lacks some of the scope of the previous work. I still enjoyed this, but it wasn't Empire Strikes Back to the first book's Star Wars, it was more random "Next Generation" episode to Wrath of Khan.
I don't think I can discuss this plot without mildly spoiling Ancillary Justice, so reader beware.
This book picks up right where the last book left off. Breq has uncovered a deep crisis within the Imperial Radch that threatens to tear the Empire apart, and at the very least could return it to the most vicious form of its colonialism which recent reforms had attempted to moderate. She is able to take command of a ship and proceed to further investigate said crisis. This takes her to Athoek Station, which seems like the jumping off point for a big quest that will delve into the big mysteries of split identities and possible alien infiltration raised by the previous novel...but instead, Sword settles in while Breq meets the locals, tries to do some reforming of corrupt colonial policies and gets involved in some old-fashioned detective work. In other words, it reads a lot like the flashback scenes of the previous work, but it lacks the interspersed bits that contained some more action, nor does it have the big revelations and big galactic-stakes climax of that book.
I'm certainly not saying this is bad, it's just not what I expected. The conflicts and mysteries of Athoek Station are interesting, and Leckie does a good job developing the place and its characters. But the first book introduced three or four really strong concepts that really hooked me in, and this book doesn't add much new to the mix or really advance the overall plot significantly. Breq also began to wear on me a bit - it's interesting that she has a lot of empathy while working on behalf of a largely unempathetic empire, and so she is always fighting for the justice that is supposed to be one of the cornerstones of the Radch. In practice, however, this involves a lot of scenes where she lectures people on why their policies are wrong (I came to refer to this, probably unfairly, as Breqsplaining). I was also bummed that the most interesting character from the last book, Seivarden, is mostly sidelined, as is a promising new character with an interesting hook named Tisarwat, who doesn't get enough to do after the early chapters either. And I'm still not entirely taken by the prose, though again, there is a good excuse for its occasional stiffness.
So, a slight disappointment, but it does set the stage for an exciting third entry, which I will be reading, thanks again to Locus SF voters.