This book is awesome. And I mean that in the formal sense of the word: my mind is officially blown. 
 There is so much to Ninefox Gambit that it's hard to figure out where to start. The story takes place in a world governed by calendrical systems: in effect, the beliefs, calendar, and observances of society create topologies that in turn affect the laws of physics and allow the use of "exotic effects," which are almost always utilized as weapons. Cheris lives within the hexarchate, which is run by six groups, each with their own distinct characteristics and symbol, from the burning suicide hawk of the Kel to the crafty Shuos ninefox. Cheris, a member of the straightforwardly warlike Kel, finds herself paired with the most infamous Shuos of all, on a mission to save the supposedly impregnable Fortress of Scattered Needles from calendrical heresy. All too quickly, she finds herself in a constant battle of wits with a formidable ally, constantly struggling to determine her true enemies. 
 One of the most brilliant aspect of the book is the way in which it places the reader within a world and a culture and a mindset so alien from our own. The hexarchate is not a pleasant place, constantly at war with all of its neighbors, ruthlessly destroying the cultures of all those it conquers, and scrupulously performing bloody "remembrance rights" to keep the calendrical systems strong. The Kel may be innately loyal, but to better fulfill their role as the hexarchate's disposable army, they are brainwashed and programmed with "formation instinct" so that they are effectively incapable of disobeying orders. Given the structure of the world, it's not surprising that the book is both dark and intense. From the perspective of the hexarchate's stultifying culture, the story tackles issues of gender and rape. Death is a constant throughout the story, and it is portrayed as brutal and grim rather than valiant and heroic. As one character thinks: "War is all about taking the future away from people." 
 Despite the dark themes, I couldn't help but find the calendrical system just plain awesome. As one character puts it: "In a sense, all calendrical war is a game between competing sets of rules, fueled by the coherence of our beliefs. To win a calendrical war, you have to understand how game systems work." The concept of a sufficiently large population's faith, belief, and rituals actually warping the physical laws of the universe is just the coolest thing ever. Full disclosure: I have to admit that I suffer from Math Envy: while I don't think I'm really capable of understanding higher mathematics, I'm utterly fascinated by the core ideas, at least in the abstract. I dropped out of topology in the first few weeks because my brain felt like silly putty. I survived first-semester real analysis by the skin of my teeth and even so, I wandered around in a daze for weeks because now I knew what real numbers actually were. This book was so fascinating that it gave me a newfound desire to try to learn topology again. 
 But even apart from the mathematical aspects, the worldbuilding is fascinatingly deep and infinitely creative: disregarded self-aware artificial intelligences who act as servitors for the hexarchate, immortality devices and the black cradle, battle formation geometries, deadly threshold winnowers, human composite technologies, much else besides. And throughout the story is a constant theme of games, and games within games. As one opponent tells Cheris, "You lost the moment you agreed to play the game on my terms, without negotiating."Ninefox Gambit is an impressively creative story brimming over with metaphor and symbolism and and analysis. If you're a fan of mathematics and mindgames, you really need to check out this book. I can't wait for the sequel. 
 ~~I received this ebook from the publisher, Solaris/Rebellion, in exchange for my honest review. Quotes are 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.