"Nobody's Man" by E. Phillips Oppenheim

Edward Phillips Oppenheim was an English novelist, and a prolific writer of best-selling genre fiction. This book takes place in the aftermath of the first World War when many countries suffered economic and political turmoil. Revolutions brought communism and socialism to power in many European countries. It is in this tumultuous time that Andrew Tallente, a middle-aged politician whose once bright career has been ruined by jealousy, retires to his small farm on the coast of Devon where he discovers his personal secretary has been having an affair with his wife. There he meets Lady Jane Partington, a progressive landowner and strong-willed modern woman who makes him rethink his world view.