The Ember Oath: A Romantasy Novel (Ashfall Academy) by Lara K. Thorne

The empire built the wall. Her brother is on the other side of it — and Lyra Vessren is going to find him, even if she has to bring the whole cliff down to do it. Five years ago, the empire told Lyra her brother died in a border accident. Then it mailed his cloak home, professionally cleaned and mended — the clumsy fishing-line stitches he'd sewn himself picked out and redone by a stranger's hand. You don't wash a dead man's cloak. You wash evidence. Now twenty years old and armed with a lifetime of pretending to be no one, Lyra has walked five hundred miles up the Ember Road to enrol at Ashfall Academy — the imperial military school where her brother was last alive, where the archives hold the file the empire's condolence letter was written to bury, and where the wrong question, asked in the wrong room, gets a girl drowned. She means to keep her head down, break into the archive, learn the truth, and vanish. Read more