I liked this book more than most other fantasy books I read this year. It drew me in from the beginning. The story is not exactly light-hearted, but -- at least at first -- it didn't lack in humor. The heroine Runin's (Rin for short) situation somewhat resembles Harry Potter's: she is an orphan with unusual talents growing up in an adopted family that mistreats and undervalues her. The family wants to get rid of her as soon as possible by marrying her off as a teen. But her talents, persistence, and cunning lets her escape her family and the looming marriage, and achieve a future that no one of her social class could dream of.
Hopefully this is not too much of a spoiler, because this happens relatively early in the book. Rin is admitted into the nation's top school, where, despite some teachers' attempts to derail her, she persists and gains exclusive, esoteric knowledge that's unattainable even for the elite students of that school. All throughout that, the book has a Harry Potter'esque "wizard school novel" feel, except that Rin is more like Hermione than Harry. Clever and doggedly stubborn, she outwits the stodgy adults that consider her unworthy of being there and thwart her at every step.
But the tone of the book completely changes in the second chapter, about a third into the novel. It changes so much that I wondered whether the first chapter and the rest of the book were initially separate novels featuring different protagonists, and only later for some reason were fused into one. The humor of the first chapter is gone, and the book takes a dark turn. The country is at war, and Rin is now a member of a small squad called the Cike, which is roughly a roving band of wizards. The Cike have supernatural powers. In this book, magic comes in a form of connecting to a god (in this nation's pantheon there are several) and asking them to do the dirty work for you. Often the practitioners of "lore", or magic, need to take consciousness-altering drugs to connect with gods.
Their magic powers, however, don't make the Cike superheroes. For all their formidable abilities, they still are unable to stand up against the vicious aggressor armies. This is part of what I liked about this book. It shows the limitations of magic very clearly. And it shows how the wizards' superpowers can lead them down a tragic path. They can't help but spiral into the ultimate arms race. Since the very beginning, Rin's old lore teacher -- the one who taught her to connect with the gods -- tells her that she should not under any circumstances try to "weaponize" them, i. e. call on their powers in a war. What the gods will unleash on Earth will be far more terrible than the damage done by war, he warns her. And, as you might expect, the Cike -- who are in their teens and early twenties, and have knowledge, but not much wisdom -- quickly get drawn into the cycle of aggression and revenge. They pull the gods into the war to exact worse and worse punishment, which, in turn, provokes more aggression from the invading army.
The dilemma is presented in the book very vividly. The aggressor is so horribly cruel that in the reader's mind there is not even a doubt that it's worth calling upon gods to destroy them -- until a wise man like Rin's teacher Jiang makes a case that maybe you really, really shouldn't. The reader gets to see the points both pro and con, and those are not strawmen arguments. They are weighty and well-balanced. True, the brutality of the enemy army can seem so excessive that it's at times ridiculous, but it's probably nothing that hasn't happened in some part of Earth at some point or another.
Being forced to choose between different evils, when it's hard to even tell which one is bigger, makes for a good tension source in a book. I liked that this book didn't have a happy ending. At most it had an ending that could be described as "not the worst possible".