Ninefox Gambit by Yoon Ha Lee
“Amid such brutal calculus, Lee (himself an Ivy League-educated mathematician) fortunately doesn’t stint on character development or plot. The protagonist is Kel Cheris, a young soldier gifted in number theory, who is summoned from the battlefield for a strange new mission. She must partner with the disgraced General Jedao, possibly the only person in the hexarchate who can help reclaim the strategically critical Fortress of Scattered Needles and stop the looming threat of calendrical rot. Problem: Jedao has been dead for centuries, executed after he went mad and slaughtered thousands of his own people. Cheris must become host to this unstable genius’s “ghost,” or preserved personality and once she does, she must immediately learn how to navigate her way through politics more ancient than the hexarchate itself. Meanwhile, if she slips even once in her self-control or calculations, her ghostly ally will drive her mad too. Or worse.
The story is dense, the pace intense, and the delicate East Asian flavoring of the math-rich setting might make it seem utterly alien to many readers yet metaphors for our own world abound…Readers willing to invest in a steep learning curve will be rewarded with a tight-woven, complicated but not convoluted, breathtakingly original space opera. And since this is only the first book of the Machineries of Empire trilogy, it’s the start of what looks to be a wild ride.” — New York Times