Her Beastly Duke by Hayleigh Mills

Briar is willing to do anything to save her twin brother from ruin and disgrace—even resort to theft. If her brother marries well, it will rescue the family and save Briar from a fate she dreads: marriage.

Lord Julius Fenton, the Duke of Berkley, is known as the beastly duke. Scarred and masked, he lives a life of seclusion, shunning society except for business matters. He never imagined wanting more—until Briar knocked the rapier from his hand in his library. She ignites an inexplicable fire within him, awakening a yearning for everything he’s long denied himself. To keep her attempted theft a secret, Briar agrees to help Julius find a duchess.
Julius is determined to find a wife with the right pedigree, while Briar remains resolute in avoiding marriage. Except the simmering tension between them explodes into something neither could have imagined…