The King’s Dragon by Sam Burns

Lord Tristram Radcliffe has a secret—he is the only dragon at the king’s court in Llangard. It’s a secret he’s kept from the knights he’s fought beside, from the ladies who bat their lashes at him, and from his closest companion, Prince Reynold. If it were to get out, he’d be banished to the Mawrcraig Mountains along with the rest of his kind, but the kingdom of men is the only one he’s ever known, and his heart lives in the stone halls of those who’d count him an enemy.
When the old king dies and Prince Reynold takes the throne, two visitors from the north throw Tristram into the middle of the ancient conflict between dragons and men. They put him on a collision course with the king’s shadow, Bet Kyston, a dangerous assassin who may want him dead or may want more of Tristram that he’d ever thought to give.
With the eyes of dragons upon him and a threat from the north creeping toward the home he loves, Tristram must weigh his allegiances before his dual legacies tear him apart.