Thuvia, Maid of Mars (Mars, Bk. 4)

"First Published - 1916. Carthoris falls in love with Thuvia, princess of Ptarth, who was rescued by John Carter from the Therns. Thuvia is stolen away by Astok, Prince of Dusar, Ptarth's rival. Carthoris follows her across Barsoom and rescues her, encountering some strange and fascinating creatures. Thuvia, unfortunately, is already betrothed to Kulan Tith, Jeddak of Kaol, ally of Helium."