Give Your Heart a Rake by Merry Farmer

Lady Siobhan O’Shea will never forgive her brother for losing her in a silly bet. Thanks to Caelian’s loss, she is now obligated to marry Rory Feeney, a man she despises. Rather than simply refuse to honor her brother’s wager, Siobhan has plans of her own, plans to teach both the odious, rakish Rory and her brother a lesson.
As a self-made millionaire, Rory has enjoyed living a life that no one from his humble beginnings could ever have imagined for him. The perfect sign of his advancement in the world would be marrying into the aristocracy, so when he wins a bet to marry an earl’s daughter, he is determined to go through with it, no matter what protests Siobhan raises.
But things take a turn for the unexpected when Rory discovers that he actually likes Siobhan’s outlandishly stubborn ways. And Siobhan secretly comes to see Rory as more than the rogue she thought he was. But can love over come pride as both of them vie for the upper hand in their marriage of convenience?