The Chessmen of Mars is an Edgar Rice Burroughs science fiction novel. In this novel Burroughs focuses on a younger member of the family established by John Carter and Dejah Thoris, protagonists of the first three books in the series. The heroine this time is their daughter Tara, princess of Helium, whose hand is sought by the gallant Gahan, Jed (prince) of Gathol. Both Helium and Gathol are prominent Barsoomian city states. The novel can be classed as a planetary romance. This genre is a subset of science fiction, similar to sword and sorcery, but including scientific elements. Most of the action in a planetary romance is on the surface of an alien world, usually includes sword fighting, monsters, supernatural elements as telepathy rather than magic, and involves civilizations echoing those on Earth in pre-technological eras, particularly composed of kingdoms or theocratic nations. Spacecraft may appear, but are usually not central to the story.