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.