I had heard really good reviews about this book from trusted sources, but what really sold me was the idea of a main character who is all genders (she's had many bodies, and doesn't identify as any particular gender). I absolutely loved Left Hand of Darkness for doing something similar, so I immediately put Ancillary Justice on my TBR list and blocked out all information about it. 
 Months later, when I finally got a copy and set down to read, I'd forgotten what I'd already heard about the book and came to it completely fresh. And it is wonderful. 
 As I was reading, I kept feeling like my mind was being blown. Not in the sense that I was confused, but the opposite - in the sense that something was suddenly making sense for me, that I was understanding a problem from a new perspective. 
 The story pretends to be about this quest that I won't bother getting into, but that's all just a premise. The story is really about identity - what makes the self? What makes an individual separate, unique? And this theme is explored from many different perspectives in both storylines. Sometimes it includes gender, sometimes not. Sometimes it includes free will/destiny, sometimes not. Sometimes it approaches it from the standpoint of cultural belonging, sometimes from shared mind belonging, sometimes from the perspective of a lone outsider. Over and over again, Leckie picks at this idea of mind and selfhood with an astonishing - and astonishingly unobtrusive - focus (I might even call it "single-mindedness," but that's a little too on-point). 
 The surface quest story reads well enough, though I'm not surprised to see some reviewers calling it "boring." It's true that there's a lot of dialogue and a lot of narrative thinking, and the action scenes - when they do crop up - lack emotional intensity. So I can understand those complaints, even as I disagree very strongly. 
 The lack of emotion, the distance of the narrator, is something that a lot of negative reviewers have commented on. This is something I found very interesting because it occurred to me early on in my reading that Breq is autism-coded. Over and over again, I felt a comfortable familiarity with how she was thinking, how she was observing and processing the emotions of those around her. And while other readers apparently felt that the book lacks in characterization, I felt like I was getting to know these characters on a deeper level than I usually do in books. It was almost like I could feel Breq or Awn in the room with me as I read. And I connected with Breq's emotional responses on a very deep level. 
 I don't know if Leckie is on the spectrum herself, but she gets it. She completely gets it. And this is the first book I've ever read where I felt like the main character was honestly, truly, like me. 
 The languages of the novel were extremely well done. I enjoyed the immigrant experience of being revealed as different or thought weird because of grammatical errors, and Breq's struggle to keep track of so many varied cultural traditions. I liked that, though English is used throughout, the narrator indicates when different languages are being used and how translations aren't always really capturing what was really said or implied. 
 The Radch single gender - she - is perfectly handled. Despite Breq thinking of all characters as 'she,' and despite her frequently misgendering other characters so that they can switch genders several times even in a single scene, I never felt confused about who was talking or acting. Leckie did a wonderful job making sure all agents were clear. The only thing that threw me is that she would sometimes have more than one character speaking/acting in a single paragraph, but I was usually only confused because of the convention. Her labelling held up well. 
 This is an amazing book. Just to give a single flaw, the Epic Battle at the very end lost some of the book's usual narrative tightness, and there were some moments where I was struggling to picture what was going on. But that accounts for a very small percentage of an otherwise fantastic book. 
 I highly recommend it for fans of science fiction and world building, particularly for anyone who is interested in novels that are more thought-experiment than action/adventure-type reads.