Eon: Dragoneye Reborn Book

Twelve-year-old Eon has been in training for years. His intensive study of Dragon Magic, based on East Asian astrology, involves two kinds of skills: sword-work and magical aptitude. He and his master hope that he will be chosen as a Dragoneye an apprentice to one of the twelve energy dragons of good fortune.

But Eon has a dangerous secret. He is actually Eona, a sixteen-year-old girl who has been masquerading as a boy for the chance to become a Dragoneye. Females are forbidden to use Dragon Magic; if anyone discovers she has been hiding in plain sight, her death is assured. When Eon’s secret threatens to come to light, she and her allies are plunged into grave danger and a deadly struggle for the Imperial throne.
Eon must find the strength and inner power to battle those who want to take her magic...and her life.

The Washington Post - Rachel Hartigan Shea

Quickly paced and full of surprising twists, Eon transcends standard fantasy fare because author Alison Goodman focuses on the intrigue—poison, secret tunnels, rebellious eunuchs—in the lush imperial palace, and on the way this young girl eventually realizes that she must embrace her female self, her "Moon energy," in order to prevail.