The Gods of Mars (Unabridged‪)‬

After a 10-year absence, John Carter returns to Barsoom. He finds himself among the Therns, a white-skinned race of self-proclaimed gods, who have for eons deceived the Barsoomians elsewhere that the pilgrimage to the Valley Dor is a journey to paradise when it is in fact a valley of death. 

This is book two of Edgar Rice Burroughs' Barsoom series.