The Accidental Duchess - Madeline Hunter

From New York Times bestselling author Madeline Hunter comes this seductive tale of a headstrong young lady, a scandalous manuscript, and the iron-willed duke determined to save her from her ruin. For fans of Mary Balogh, Eloisa James, and Julia Quinn.
When Lady Lydia Alfreton is blackmailed over the shocking contents of a manuscript she once wrote, she must go to the most desperate of measures to raise the money to buy back the ill-considered prose: agreeing to an old wager posed by the arrogant, dangerous Duke of Penthurst. At least Penthurst is a man she wouldn't mind fleecing—and she's confident she'll win.
Penthurst long ago concluded Lydia was a woman in search of ruinous adventure, but even he is surprised when she arrives at his house ready to bet her innocence against his ten thousand pounds—a wager he only proposed to warn her off gambling.
When she loses to a simple draw of the cards, Lydia is shocked. Now, her problems are twofold: a blackmailer determined to see her pay and a duke determined to tame her rebellious ways. One misstep and Lydia could find herself ruined—or bound to the seductive man who would make her his duchess.