Thuvia, Maid of Mars
Author: first_name: Edgar Rice
last_name: Burroughs
Language: English
Year: 1916

In this novel the focus shifts from John Carter, Warlord of Mars, and Dejah Thoris of Helium, protagonists of the first three books in the series, to their son, Carthoris, prince of Helium, and Thuvia, princess of Ptarth. Helium and Ptarth are both prominent Barsoomian city state/empires, and both Carthoris and Thuvia were secondary characters in the previous two books. (Summary by Wikipedia)