The desperate viscount

Lord St. John had expected to become a duke but his great-uncle married late and had a son. Which left Sinjin in a very difficult situation, since he had a penchant for gambling and women. He chose to marry a tradesman's daughter, Mary Pepperidge, because he had met her previously. But the shy, biddable woman turned out to have unexpected depths. Regency Romance by Gayle Buck; originally published by Signet