Scandal in Spades by Wendy LaCapra

The Marquess of Bromton has just learned that he’s a bastard. Feeling his honor is at stake, he attempts to bestow his estate upon a rightful heir by manipulating a high-stakes card game. But the winner demands more than Bromton bargained for—a marriage…to his spinster sister. Lady Katherine may be the least marriageable lady in all of England, but a child of their union would be a rightful heir…

Scandal has hardened Lady Katherine and narrowed her world to duty and family. There’s nothing to be trusted in the Society she left behind…especially not the imperious marquess with his single-minded pursuit. Or his knee-weakening kisses.

Except, the more their connection deepens, the more Bromton surprises Katherine. But the truth about their courtship could destroy everything…