Eon: Dragoneye Reborn by Alison Goodman

Book SummaryThe story follows Eon, a sixteen-year-old girl who has spent years masquerading as a twelve-year-old boy. In this Asian-inspired fantasy world, females are strictly forbidden from using Dragon Magic upon penalty of death. Eon trains heavily in swordplay and magic to compete to become a Dragoneye apprentice—a powerful human conduit capable of channeling the elemental energies of one of the twelve ancient spirit dragons. When her true identity threatens to leak, she is thrown straight into a high-stakes deadly struggle for the Imperial throne.