The Assassin and the King by Layla Moran

Born into a legendary bloodline of assassins, Thorne has never questioned orders—until now. Tasked with eliminating the crown prince on the eve of his coronation, Thorne infiltrates a glittering masquerade ball, his blade hidden and his resolve sharp. But the prince is nothing like he expected: charming, clever, and disarmingly kind. Drawn into the prince’s magnetic orbit, Thorne begins to lose sight of where duty ends and desire begins. As their connection deepens, he uncovers a web of deception that makes him question everything—including the truth behind his mission, and the loyalty he’s spent his whole life trying to prove.