Undeniable by A. S. Roberts

Secret lives.He knows all about those.She’s just now learning the ropes.Jack Carpenter’s family thinks he’s a high flyer on the London stock market, but that’s far from the truth. Illegal, bare-knuckle fighting earns him a comfortable lifestyle–almost too comfortable.
When a notorious gangster can’t pay what he owes, he gives Jack an offer he can’t refuse: ninety days with any woman of his choice, until the bet is paid off. One night and one tragic accident later, Lily Green’s perfect life ends. Suddenly, her father’s double life implodes into her own. Not only was her father a criminal, but his debts are now hers.

Unfortunately the only thing she has to offer, is herself. Lily becomes the consolation prize for a man whose very existence is everything she detests. Incidentally, that same man is also the first man she ever let touch her.Ninety days of undeniable passion… will either of them be able to resist?