Originally published in 1878, Is He Popenjoy? is a delightful comic novel written late in the career of author Anthony Trollope. The plot revolves around the themes of property and inheritance, as the relatives of the Marquis of Brotherton question the legitimacy of a foreign-born heir to the family estate.

Lord George Germain, as the younger brother of the marquis, can neither inherit the family title nor enjoy the income from the estate. He occupies the ancestral home, Manor Cross, only by grudging permission of his elder brother, who lives abroad. But he does find happiness in his marriage to Mary Lovelace, the sweet-natured young daughter of the Dean of Brotherton, who brings a family legacy that provides an immediate solution to his financial problems.

Lord George's new-found contentment is thrown into turmoil, however, when the marquis announces that he is returning to England, having married an Italian widow who has borne him a son—Lord Popenjoy, as the heir to the title is traditionally known. Lord George, his wife, his mother and sisters, must therefore leave the house to make way for his brother.

On his return, the marquis shows himself to be a despicable bully who treats his family and all around him with supercilious condescension. But Mary's father, the Dean, suspects that the marquis' son may not be a legitimate heir—that Popenjoy may in fact not be Popenjoy—and determines to make enquiries as to the validity of the marquis' marriage and his son's claim to the title.

The story is full of entertaining characters and twists and turns, including love affairs, jealousy, and the rights of women—all told with Trollope's liberal satire and entertaining wit.