The Earl of Her Dreams by Anne Mallory

Facing the choice of flight or a wedding she cannot abide, Kate Simon has chosen to flee. Disguised as a boy, she takes refuge in a roadside inn, and finds herself rooming with intensely secretive Christian Black. Kate is breathless in the presence of this handsome, mysterious rogue whose piercing gaze seems to strip her naked. But neither suspects that a savage storm and a murder will draw them closer together still. But not the passion in their hearts

Christian dares not let anyone learn of his haunted past—or that he is, in truth, the Earl of Canley—especially not a slip of a girl whose masculine attire cannot disguise the exquisite female form beneath. But now that destiny and a dastardly crime have united them, Christian can no longer contain his desire to taste the nectar of Kate's sweet kiss. Danger certainly abounds, but the gravest peril might be resisting a once-in-a-lifetime passion that can heal all wounds.