To Marry a Lord by Jenn Langston

Hannah Dobson, Countess Rivers, thought all her troubles had died with her husband. She’d been wrong. When her husband’s nephew, Lucius, inherits the title, she knows their mutually hostile relationship could prove detrimental. However, Lucius requests her help in deciphering a puzzle her late husband left for him. As they work together, Hannah realizes there is more to Lucius than she originally believed.
As the Earl of Rivers, Lucius Dobson has many responsibilities that he must attend. Unfortunately, with his uncle’s ridiculous game, he deprived Lucius of the means to see to his duties. The decision to request Hannah’s assistance had been simple, but with their history and his overwhelming attraction to her, keeping his mind on their task proves difficult. In addition, he must keep the truth regarding her marriage to his uncle a secret. If she were to find out, she’d never forgive him.
While the search for clues to the puzzle continues, Hannah grows more attached to Lucius and fears it’s already too late to protect her heart. Left with no options, she enlists her friend’s help at the House of Reform. Once Lucius finds a bride, she can put this predicament behind her.