Empire ascendant is the second book in the Worldbreaker series, and it does not work as a standalone, so you should go and read the first book, The mirror empire, before you do anything else.
Story time: The first time I saw Kameron Hurley's name, it was as a Hugo award novel nominee - one that I chose to ignore, because I saw the title God's war and it looked like yet another sorta military SF series and I didn't urgently need another one of those. I probably also assumed Kameron was male, which she is not, and now I know that whatever she writes, it is never going to be a mere "yet another". Really. I still haven't read God's war or the rest of that series, but I can say very definitely that I will, because I have become a Kameron Hurley... fangirl? Devotee? Acolyte? I honestly can't pick an appropriate term. If you follow this author in social media, you'll understand. Her upcoming book, The geek feminist revolution, speaks volumes - with just its title.
I bought The mirror empire when it was first published, and then, unfortunately, it got shoved back indefinitely in my to-reads. It takes a certain time and energy to get started on high fantasy things - at least it does for me. The time didn't come until quite recently, when I finally started on it, and found a story with characters more broken, violence more brutal, and world more unforgiving than... I'm not going to say it. Let's assume that statement ends with "...Any natural comparison in the world of gritty high fantasy."
It has a lot of female characters. It has characters who are careful about preferred pronouns, cultures with different ideas and terms for various genders. "Culture crash" is a kind of giggly undercurrent for the whole story, considering the nature of the mirror empires. The parallel world thing can be difficult to sort out in a novel, and maybe you do need to pay some careful attention at the start - but I thought Hurley did it well, and I was never really confused about what world anything took place in. Unless she deliberately tricked me, of course, which I'd applaud.
Anyway, with a second book in a series, the one this review is actually for, you already know the characters. I was impatient and agitated to see what became of Lilia and Roh, Ahkkio and Nasaka, Anavha and - you know what? Zezili is around. That was a little surprising, given how her last chapter in the previous book turned out.
Her chapters are by far the most interesting to me, this time. Like many other high fantasy series, these books employ a large set of different viewpoint characters, whose stories occasionally weave into one another. Zezili still insists, is still actually quite convinced, that she's just a bullheaded soldier, one who knows war and death and does not care much for wrapping her mind around things like politics and philosophy and that sort of thing. But her actions betray her. She has made a decision no one asked her to make, and she never doubts herself or the path she's chosen, no matter how much it mangles her.
Zezili is not at all a good person - we know too much about her household and culture to allow that particular illusion - I can hardly say she's likeable, but she's certainly interesting - and her discoveries are terrifying.
And I like Lilia, who is no less of a hardass than Zezili, though she may not look it. Most of the time, it's heartbreaking to see her come up with brilliant stategies, only to be thwarted by her people's lack of respect - or faith - in her. Along with Lilia we find Taigan, who might be the single most unpredictable character around, and would be even without the fluctuating gender phenomenon.
The magic system in these worlds depends on the stars - para and tira and sina offer different kinds of power to those who are born with the ability to draw on them, and these magic wielders depend on their corresponding stars. But we know, after the previous novel, it's a different star on the rise, its effects threatening to shatter the world. Or, well, worlds.
As always, I find it near impossible to talk meaningfully about plot in a second-book-in-series. So I'll say this to those who already read The mirror empire: Yes, you want to read this too, and no, you will not be disappointed.
And if you didn't read The mirror empire - you should. Now. Go!