The School for Brides (School for Brides #1)
Cheryl Ann Smith

Miss Eva Black spent her life concealing her mother's past as a courtesan. Now a spinster, her beauty hidden away under a dour disguise, Eva spends her days schooling courtesans to be suitable wives. But one vengeful duke does not appreciate Eva stealing his mistress and transforming her into a lady. His vengeance won't be satisfied until he seduces Eva into becoming what she detests most: a courtesan.
Nicholas, the Duke of Stanfield, is furious with this woman who frees courtesans from bondage. His revenge? Upend Eva's world by buying her debts and striking a scandalous bargain: She must serve as his mistress' replacement. But he doesn't expect her to be a woman of such beauty and secrets—or to have a past that not only endangers Eva herself, but everyone whose life she has so intimately touched.