What is the theme in Angle of Repose by Wallace Stegner?

Marriage is a strong theme in the novel. Lyman is writing the novel about his grandparents to understand them and how their marriage lasted for sixty years. They had many hardships, but overcame them for the sake of their marriage. Lyman’s own marriage has ended in divorce. His wife left him for the surgeon who cut off his leg. Lyman wants to understand how his marriage ended and his grandparents stayed together through tragedy. Looking at his grandparents marriage, helps Lyman to forgive his wife and start healing his wounds.