Ninefox Gambit by Yoon Ha Lee is a book I did not think I'd enjoy — and was proven wrong. I'd heard there was math in it, and had assumed it was boring. Instead, it was part of a complicated and well-thought-out world, where calendars, religion and formations combine to produce magic-like effects used in warfare. Math is a part of the world, but you are not going to be hit with equations. Instead, you are shown an unfolding and highly political world, where religion is enforced to create military superiority, and the 'grunts' of the military have an enforced group-mind.
In this world, we are presented with an everywoman, Cheris, who has to team up with the ghost of war-criminal and military genius, Jedao, to protect her world's continued survival. Ninefox Gambit is a book of average novel length, with a reading time of about seven and a half hours, with reading time slowed down by the many factions and concepts unique to this universe that one needs to digest.
Characterization is great, with characters each having their own narrative voice, different sets of knowledge and strengths and weaknesses and believable arcs, goals, and social groups. The main power players in this world don't bleed together into generic ideals of good or bad. The characters serve the plot, helping make it feel natural and not contrived, for all its complexity. Plot twists you didn't see coming appear as shocking, and yet fitting for the characters involved in hindsight. The world itself is complicated and well-thought-out, and the world helps inform the characters and mold them, making the setting truly integral to the story in ways that some sci-fi books miss. It's not just a 'strange' world; it's a place the characters inhabit.
This book was a joy to read, and is definitely one I would recommend for people who enjoy sci-fi, space battles, or military fiction. It's a book that will easily bear the brunt of repeated read-throughs without feeling like dull repetition.