The Priory of the Orange Tree: Samantha Shannon

An enthralling, epic fantasy about a world on the brink of war with dragons - and the women who must lead the fight to save it.
The House of Berethnet has ruled Inys for a thousand years. Still unwed, Queen Sabran the Ninth must conceive a daughter to protect her realm from destruction – but assassins are getting closer to her door.
Ead Duryan is an outsider at court. Though she has risen to the position of lady-in-waiting, she is loyal to a hidden society of mages. Ead keeps a watchful eye on Sabran, secretly protecting her with forbidden magic.
Across the dark sea, Tane has trained to be a dragonrider since she was a child, but is forced to make a choice that could see her life unravel.
Meanwhile, the divided East and West refuse to parley, and forces of chaos are rising from their sleep.