The Chessmen of Mars

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. (Wikipedia)