Ancillary Mercy is the third in Leckie's Imperial Radch trilogy following the quest of Breq, who used to be the AI of the warship Justice of Toren and has now been reduced to a single body, to inconvenience Anaander Mianaai, the tyrannical ruler of the Radch, whose multiple bodies have turned against each other and split the Radch empire up into chaos.
Perhaps I just wasn't concentrating very hard, but Ancillary Mercy felt kind of...shapeless? It's centred on the fact that Anaander, the part of her hostile to Breq, has entered the Athoek system, where Breq's new ship, Mercy of Kalr, is stationed, and is vaguely threatening both the planet of Athoek and, more urgently, the station in orbit around it. Meanwhile, on the station itself, some of the richer residents of Athoek station are stalling the refit of an area that was flooded during the second book, which was inhabited mainly by Ychana, an ethnic minority seen as undesirable; and the dangerous alien Presger have sent a translator to Athoek to find out what happened to their last one.
There's a lot of politics, as there was in the second book, and the varying strands of the novel - the racism of Athoek station's upper class, the threat from Anaander Mianaai, the interference of the Presger - all tie up nicely in its conclusion. It's a book about various kinds of oppression - oppression which hardly ever stems from actual bad faith but from carelessness and thoughtlessness and a blindness to the way things are. In particular, the discussion about AI rights, which has been bubbling under for the first two books, surfaces properly (and satisfyingly) here.
For a book about someone who used to be a hive mind, it's also very singular. By which I mean that it takes place almost entirely in a single system, focusing solely on Athoek's concerns; Breq, in fact, firmly rejects offers of help from captains stationed in nearby systems. It focuses on making just this one corner of the empire a bit safer, a bit more just; no promises are made for the rest of it, there are no universe-saving grand political gestures. It's realistic about the political reach of Breq and her crew.
Stylistically, and this I think is why my mind finds it hard to remember specifics about it, it's quite oblique: as in, its characters will discuss something without being specific, and I think we as readers are supposed to pick up what theyre talking about. Which means you sort of have to work at reading it, to go back and pay attention to inflection and implication - just as its characters do, I suppose, in their various political maneouverings.
I liked it, as much as I liked the previous books, but I don't think I was quite in the right mood for it. I think there's a lot of interesting stuff going on here; it just hasn't made that much of an impression on me.