The Ugly Princess — Elizabeth K. Burton

Christopher Evergild, like his father and his grandfathers before him, had trained all his life for one thing: to be the Royal Champion of Abernal and maintain the peace with the strength of his arm. Then the king dies at his wedding feast, and his heir is a woman exiled to a mountain keep as an infant -- a woman reputed to be so hideous only trolls can bear to look at her. Plots to replace her sprout before the king's corpse is cold, but Chris's duty is clear. How is he to know doing the right thing will change his life forever?