The Duke by Katharine Ashe

Katharine Ashe continues her lush and sensual Devil’s Duke series with a sweeping story of unbreakable love
Six years ago, when Lady Amarantha Vale was an innocent in a foreign land and Gabriel Hume was a young naval officer, they met . . . and played with fire.
Now Gabriel is the dark lord known to society as the Devil’s Duke, a notorious recluse hidden away in a castle in the Highlands. Only Amarantha knows the truth about him, and she won’t be intimidated. He is the one man who can give her the answers she needs.
But Gabriel cannot let her learn his darkest secret. So begins a game of wit and desire that proves seduction is more satisfying—and much more wicked—the second time around…