The Europeans (Penguin Popular Classics)

Eugenia, the daughter of American expatriates, is the morganatic wife of a German prince, who is being urged to divorce her in favor of a state marriage. She and her artist brother, Felix, travel to Boston to meet distant cousins relatives, partially in hopes of making a wealthy marriage.

Its wit, gaiety, and what Rebecca West calls its "clear sunlit charm" have made this masterly short novel one of the most popular of James's novels.