If You Deceive by Kresley Cole
Ethan MacCarrick, the eldest and most wicked of the MacCarrick brothers, tricks lovely and innocent Holly Weyland into thinking he's eloping with her; instead, he takes her to his wind-tossed, seaside estate in the Highlands, planning to seduce her and make her his mistress until he tires of her. Yet just when Ethan realizes he can't live without this goldenhaired lass, Holly discovers his deception. Can he convince her that he's had a change of heart, or is it too late?