If The Wheel of Time wasn't also nominated for the Hugo this year, I'd say that Ann Leckie had an excellent shot at becoming the fifth female author to win both the Nebula and the Hugo for the same book. Ancillary Justice is well-written with good characters and a compelling plot, but, most importantly for an award-winning sci-fi book, it is also full of challenging ideas, including a unique take on gender.
Ancillary Justice tells the story of the last remnant of an ancient spaceship in a human body, determined to kill the multi-bodied leader of the universe for reasons that are initially unknown. The narrative is split between flashbacks, explaining why our spaceship protagonist is on this mission, and "present day" events, where she is hunting down the only method of killing this ruler while fighting for survival herself.
The first few chapters are very confusing. Ancillary Justice errs on the side of "we'll throw you in the deep end and explain everything later," and it was a little too far into the deep end for my tastes. Who is this person? What are they doing? Wait, they're a ship? How are they a ship and also a person? What is going on? Why are we in a flashback now? The opening pages made my head hurt, and not in an intrigued sort of way. But once the book offers more explanation and eases the reader into the world more, the story becomes intriguing, and then tense, and then intense, with lots of action and character growth and compelling emotion to keep you turning the pages.
But the most compelling and interesting part of the novel, to me, is its treatment of gender. It isn't important to the plot, it's only mentioned a few times by the protagonist, but after the whole "this person is a spaceship" confusion, its the most memorable element of the novel by far.
Our protagonist doesn't see gender, and so refers to absolutely everybody in her thoughts as "she." This is, of course, far more interesting than if she referred to everybody as "he," since that would just make it a fairly traditional sci-fi/fantasy story. The protagonist struggles to correctly gender other characters in her dialogue with them, pointing out that different races and cultures have so many different ways of marking "male" and "female" that its almost impossible for an extensive traveller to guess which is which.
This gives the book a Left Hand of Darkness-type feeling, as it slowly trains the reader to stop defining the characters by gender (except this time, the "default" is a she, not a he). But when I say "slowly," I mean slowly. I spent a lot of the book trying to figure out which characters were male and which were female, so that I could picture them "properly." Occasionally other characters will refer to people as "he" instead of "she," and that feels like a vital and hard-won nugget of information: now we know that this character is definitely male or definitely female. Except, as the main race of people in the book don't differentiate between gender at all, this isn't a definite answer but simply a revelation of how one particular character views another's gender.
It should be simple -- everyone's referred to as "she" and gender doesn't really matter -- but it took a long time for me as a reader to accept it. The book's characters resisted categorization every step of the way, and I still wanted to know what box I should fit them into. This got particularly ridiculous when it came to the ruler of the universe, who is thousands of years old and controls thousands of bodies. And yet, I still wondered: he or she? It was uncomfortably revealing to see how much my brain relied on gender when it was suddenly taken away.
I would recommend Ancillary Justice for its challenging take on gender alone, but, luckily, it's not a novel that's all concept and no plot. Its background gender ideas are supported by compelling and evolving character relationships, by a strong plot and plenty of tension and action and an explosive finale. It's a novel that challenges the reader, and that isn't always comfortable to read, but it aims to grip and entertain its readers too, and it succeeds on all levels. Highly recommended!