The Duchess — Jude Deveraux

Claire Willoughby was a modern American girl of the late 1800s--fresh, practical, energetic, and wide-eyed with curiosity. A clause in her grandfather's will said that she must wed an "acceptable" man to keep her millions, and blond, handsome Harry Montgomery, the eleventh Duke of MacArran, was perfect. He owned a historic castle, he looked manly in a kilt, and he was as much a titled Scotsman as Bonnie Prince Charlie himself.
Their engagement was quickly announced, and Claire--her future as a duchess assured--set off with her entire family to meet the Montgomery clan in Scotland. Bramley Castle was a damp, chill place, overflowing with eccentric Montgomery relatives. But there was also Trevelyan, a curious, brooding man of great mystery who lived in secret in the most ancient part of Bramley. Whoever he was, he wasn't at all like Harry: Trevelyan was the most exasperating, arrogant, know-it-all of a man Claire had ever met. And the most fascinating...