The dragon's price Transference trilogy, book 1.

Fans of Julie Kagawa's Talon and Renee Ahdieh's The Wrath and the Dawn will devour this action-packed fantasy adventure about a girl who chooses to surrender herself to a deadly dragon rather than marry an enemy prince. When two warring kingdoms unified against a deadly dragon laying waste to both their lands, they had to make a choice: vow to marry their heirs to one another, or forfeit their lives to the dragon. Now, centuries later,...