She was probably male, to judge from the angular mazelike patterns quilting her shirt. I wasn’t entirely certain. ... Radchaai don’t care much about gender, and the language they speak — my own first language — doesn’t mark gender in any way. This language we were speaking now did, and I could make trouble for myself if I used the wrong forms. It didn’t help that cues meant to distinguish gender changed from place to place, sometimes radically, and rarely made much sense to me. [loc.63]
I read this because it's on the 2014 shortlist for the Arthur C. Clarke Award, which I was discussing at Eastercon.
Much has been made of the use of gendered pronouns in Ancillary Justice. One Esk (or Breq, the narrator's 'human' name) uses the female pronoun indiscriminately -- uncomprehendingly -- for all humans, with ... surprisingly few consequences. Breq doesn't care about gender or sexuality, and so her narrative glosses over aspects of the story that might be foregrounded by another narrator. One or more of the sexual / romantic relationships in the novel may be between characters of the same gender, but there is insufficient evidence -- and, frankly, it doesn't matter.
More intriguing is the blurring of first-person singular and plural: 'I', and 'we'. Breq is the sole remaining ancillary of Justice of Torren, a millennia-old, AI-controlled starship. The ancillaries, colloquially known as corpse soldiers, are the Radch Empire's footsoldiers, the zombified husks of annexed populations, animated by AIs. So in one of the threads in Ancillary Justice we encounter One Esk, a detached unit under the command of Decade Lieutenant Awn. In another thread the narrator is Breq, still mourning Justice of Torren, and possibly more than a little insane. Breq and One Esk are the same person, except that in One Esk's story the pronoun 'I' can refer to One Esk, or to another ancillary, or to Justice of Torren.
Justice of Torren loves music. One Esk can sing harmony: "I opened three of my mouths, all in close proximity to each other on the temple plaza, and sang with those three voices, “My heart is a fish, hiding in the water-grass…” " [loc.373]
Breq knows who destroyed Justice of Torren: Anaander Mianaai, Lord of the Radch, who dwells in a thousand bodies and rules supreme. Anaander Mianaai was also responsible for the death of Lieutenant Awn, for whom One Esk (or Justice of Torren?) had complex emotions. To vow revenge on Anaander Mianaai is to wreak destruction on the whole interstellar empire. But Breq knows of a device ...
Breq's search for the person who possesses the solution is complicated by Seivarden, a crew member from a thousand years ago, who's spent centuries in cryosleep and woken to find the whole of the Radch has changed beyond recognition. Breq encounters Seivarden near death, in the snow: the two have unexpected, and largely positive, effects on one another. Because Breq does have emotions, though not human ones: "Without feelings insignificant decisions become excruciating attempts to compare endless arrays of inconsequential things. It’s just easier to handle those with emotions." [loc.1199] Indeed, the whole novel could be said to pivot on Breq's / One Esk's / Justice of Torren's emotional reactions to various humans.
I find it hard to review this book without rambling, because I keep remembering new aspects that I loved. It reminds me of Iain M Banks' Culture novels and of Justina Robson's inhuman Forged, in Natural History. Ancillary Justice deals with identity, loyalty, vengeance and war: it's cinematic in scope and devious in nuance: it is, bah, the first in a trilogy, but stands alone. Very highly recommended.