I picked up Ancillary Justice from the local library on recommendation from some folks online. It was a good choice.
The book centers around the military and political structures of the Radch. The main character is one of the Radchaai soldiers who is no longer in service, and as the reader learns fairly quickly, not actually human either. The Radchaai ships are run by artificial intelligence minds that make use of multiple bodies, and the protagonist (who goes by Breq) is a final survivor of one such.
Very little of all this is explained to the reader directly, but rather is gathered as the story follows Breq's travels while also exploring memories of the (relatively) recent past. This approach means leaving a lot of the history unexplained, and it's possible some is actually wrong since we're seeing it only from Breq's perspective. I like the approach, though, as it keeps the reader curious and adds a sense of mystery as the story unfolds.
None of this is to say that Ancillary Justice is only about the big picture. Individuals drive the story, as they come into contact with Breq. Character development is a large part of the book's progression, mostly notably Breq and Radchaai ex-officer Seivarden. Motivations aren't always clear - even to their owners - but as the story progresses, gradually enough is revealed to explain (or at least imply) the reasons behind what everyone does.
Leckie does an excellent job of making the different cultures come to life as the characters encounter them. The Radch's largely fatalistic religion is described in detail, as is their highly stratified class-based family structure. The conquered regions keep much of their own unique structures as well, which come into play as the story moves through those areas.
One particularly noticeable aspect of Radch culture is their use of feminine forms for all people - she, her, sister, aunt, etc - regardless of gender. This causes confusion to Breq's AI thought processes when she's forced to use other languages that distinguish gender. It also caused me as a reader to think twice about some passages. We make some subconscious assumptions based on gender, intentional or not, and so more than once I found myself having to consciously adjust how I interpreted the writing when something didn't match my expectations. It's an interesting literary device and I'm glad to have encountered it, as an opportunity to examine just how much is implied by gender in my own culture.
Ancillary Justice won a whole lot of awards in 2013-2014, and they're well deserved. I'm looking forward to the sequels.