What is the theme in Brokeback Mountain by Annie Proulx?

Shame is another theme in the book. Ennis's internalization of the belief that homosexuality is indecent and punishable by death causes him to be ashamed about the intensity of his feelings for Jack. At the beginning of their relationship on the mountain, he insists that he is not “queer,” that their feelings for each other are not indicative of his sexual orientation.