This new novel has received rave reviews and awards (Arthur C Clarke and Nebula Awards so far), so was selected as one of the monthly reads by the Classic Science Fictiondiscussion group. This is a story in which the circumstances are only gradually revealed, some of the major revelations occurring late in the book. So if you prefer to discover everything as the author drip-feeds it, it's best to avoid reviews like this one. Suffice it to say that after a slow first half, the story gathers pace and turns out to be an original and intriguing tale.
To explain the context some spoilers are necessary but I'll avoid any major ones.
Ancillary Justice is set in a far future in which humanity has spread over a large volume of the galaxy, living uneasily alongside a powerful alien empire, the Presger. The human zone is ruled by the Radchaai in general and the immortal Anaander Mianaai in particular, relying on a fleet of powerful starships inextricably linked to their Artificial Intelligences and given names accordingly (in this respect, reminiscent of Iain M. Banks' Culture novels). Each ship carries a force of soldiers, mainly ancillaries: captives who have been given various enhancements to turn them into super-soldiers but have had their personalities wiped, being replaced with advanced fighting skills and an absolute obedience to the Radchaai. They are mentally linked to each other and to their ship, and are considered to be no longer human.
The story is told in the first person by Breq, whom we soon learn is an ancillary from the One Esk fighting unit of the starship Justice of Toren. Uniquely, she has been separated from her ship for nineteen years. Now on a remote, frozen planet, she rescues from death a drug addict called Seivarden, a Radchaai former starship captain who had escaped the destruction of his ship in a survival pod and had been recently found – a thousand years later (echoes of Campbell's Lost Fleet here, but Seivarden is no hero). Breq is on a mission, but exactly what and why we only discover later in the story.
Reading this book requires some concentration since there are two aspects liable to cause confusion. One is that the story frequently hops between events in the present and the past. The other is the question of gender. The Radchaai language does not distinguish between male and female, and Breq refers to everyone as "she" regardless, including Seivarden (although we know from the start that he is male). In fact, we only know that Breq is female from a remark made by a non-Radchaai at the start of the book. Working out the gender of other characters requires a degree of guesswork, since Breq frequently can't tell herself.
I am not sure whether this gender-blindness is just a gimmick, or if the author has a serious point to make. It does deflect attention away from all of the usual gender prejudices and male/female interaction issues that fill most novels, but on the other hand Jack Campbell – to give one example – achieves that quite effectively in his Lost Fleet series (the first one, anyway; all I've read so far) without concealing the gender of the characters.
The ending is satisfying in that it brings Breq's mission to a conclusion while still leaving plenty of scope for sequels, and in fact we learn in an interview attached to the end of the novel that the author is planning a trilogy. I wasn't at first sure that I was going to like this story, as the pace is slower than I prefer and the gender ambiguity is confusing and somewhat irritating. However, the writing quality is very good – I was reminded of Ursula Le Guin – and I was intrigued from the start, so I persevered. My involvement in the story and the characters gradually increased to the point at which I didn't want to put the book down, so I will certainly be looking out for the next volume.