Ninefox Gambit 
 was one of the best books I read in 2016. Raven Stratagem might be even better. This whole series is utterly, gloriously, astoundingly brilliant. 
 Welcome to the world of the hexarchate, where total participation in rigid ritual not only keeps control of the population; it also warps the topology of reality to create "exotic effects" that keeps the hexarchate in power. The hexarchate is ruled by six factions: the Rahal, who make the rules; the Vidona, who enforce them with torture; the Andan, who control the culture; the Nirai, who provide mathematical and scientific technology; the Shuos, who act as spies, assassins, and bureaucrats; and the Kel, who are the military wing of the hexarchate. All but the Shuos depend upon an exotic effect to remain in power, from Rahal scrying and mindreading to the Nirai spacefaring mothdrive to the overwhelmingly powerful Kel military formations. Heretics are therefore a tangible, literal threat: not only do they threaten to disrupt the loyalty of the populus; they also weaken the hexarchate's exotic effects that drive the hexarchate's technology, military, and society. 
 Raven Stratagem starts where Ninefox Gambit leaves off. It introduces a cast of highly empathetic characters and explores the perspectives of several of the antagonists of the previous book. The story also expands its powerful exploration of gender fluidity. While the last book was told almost entirely from the Kel perspective, Raven Stratagem provides quite a bit more of the Shuos and even the Nirai perspectives. Our previous Shuos experience was almost entirely limited to the crazy undead mass-murdering General Shuos Jedao, who is occasionally let out of his immortal unrest in the Black Cradle to possess a Kel "volunteer" and use his scheming brain to win their wars. I adore the Shuos; it turns out they're not just assassins and spies; they're also the bureaucrats and administrators because 
 "A properly guided bureaucracy is deadlier than any bomb." 
 The Shuos are renowned for turning everything into a game and are charmingly unexpected; for instance, the leader of the Shuos faction has a tendency of knitting during scheming sessions. 
 As with Ninefox Gambit, one of the main themes of the novel was agency. Kel are imbued with "formation instinct" that irresistibly compels them to unquestioningly obey their superiors. The few "crashhawks" for whom the programming has failed are constantly under suspicion by their superiors because they can choose not to obey. The hexarchs are increasingly out of touch, off planning new sadistic "remembrances" and chasing immortality even as their people are being invaded by the savage Hafn. As one character thinks: 
 "At some point you had to ask yourself how much legitimacy any government had that feared dissension within more than invasion without." 
 The world of the hexarchate is brutal and unfeeling, the people kept under martial law and in constant fear of the Vidona. But overthrowing the hexarch also means destroying all of the technology built upon its exotic effects, and what if it is replaced with something even worse? As one character says: 
 "You know what? It is a shitty system. We have a whole faction devoted to torturing people so the rest of us can pretend we're not involved. Too bad every other system of government out there is even worse. [...] If you have some working alternative for the world we're stuck in, by all means show it to us without spelling it in corpses." 
 There are a lot of thought-provoking themes in Raven Stratagem, but they don't get in the way of the character development or the action. I was utterly captivated by the story's twists and turns, and I'm only a little ashamed to admit that I fell for one of them. (view spoiler)[Initially, I'd assumed that Cheris was in charge and playing Jedao, bolstered by their obvious care for the servitors, but as the story proceeded and they did things like enslave the Kel and let the Mwennan die without blinking and use a program for simple mathematical calculations, I began to wonder if the Jedao part had eaten the Cheris part. At some point, I lost sight of the title--"Raven" Stratagem clearly points to a scheming Cheris. I'm impressed that the book got me to lose faith while still making the big reveal feel utterly natural. Bravo! (hide spoiler)] If you were a bit overwhelmed by Ninefox, then you'll be relieved to hear that Raven is much less math-heavy, focusing more on characters and worldbuilding. We get a view of the inner workings of the hexarch from Shuos Mikodez, we finally get a glimpse of the mysterious and somewhat horrifying Hafn, and the ending is utterly satisfying while leaving me desperate for more. I absolutely cannot wait to get back to the world of the hexarchate. 
 Yours in calendrical heresy, 
 Carly 
 ~~I received this ebook through Netgalley from the publisher, Rebellion/Solaris, in exchange for my honest review. Thank you! Quotes were taken from an advanced reader copy and while they may not reflect the final phrasing, I believe they speak to the spirit of the novel as a whole.~~ 
 Cross-posted on BookLikes.