The Heritage of the Desert by Zane Grey

Published in 1910, this was Zane Grey's first western novel. It received wide and unanimous praise for its powerful portrait of the land and the men and women of the Southwest.
A lovely girl, who has been reared among Mormons, learns to love a young New Englander. The Mormon religion, however, demands that the girl shall become the second wife of one of the Mormons--Well, that's the problem of this great story.