The Priory of the Orange Tree by Samantha Shannon

From the internationally bestselling author of the bone season, a trailblazing, epic high fantasy about a world on the brink of war with dragons – and the women who must lead the fight to save it. A world divided. A queendom without an heir. An ancient enemy awakens. The house of berethnet has ruled inys for a thousand years. Still unwed, queen SA br An 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 SA br An, secretly protecting her with forbidden magic.