Love-at-Arms-Rafael Sabatini

Ralph Pendrel of New York City is bequested an 18th century house in London. He travels back in time and meets an ancestor of the same name. A triangle then follows, with new-Ralph engaged to old-Ralph's fiance, Molly Midmore, but in love with her sister Nan. James wrote the novel in fits and starts, and never finished, but fortunately for us readers, he left extensive notes. - Summary by Mark Leder