Cold-Hearted Rake by Lisa Kleypas

Charming rake Devon Ravenel inherits an earldom. But the decrepit estate is deep in debt, and the late earl’s widow and three sisters still occupy the house. His drunken brother West rides the land while Devon seeks financing in London. Kathleen, still Lady Trenear, knows better than to trust a ruthless scoundrel like Devon. But their fiery attraction is undeniable.