What is the theme of So Big by Edna Ferber?

Edna Ferber's So Big is an enduring American classic published in 1924; its complexity reveals more than a single theme.
A theme that is primary in the novel, however, is the value of beauty in one's life, regardless of one's financial situation. Selina, the novel's heroine, becomes a teacher, a farmer's wife, and after the death of her husband, a single mother and farm owner. Her financial circumstances notwithstanding, she is able to find beauty and satisfaction in both the ordinary and the extraordinary in her life. When her son decides to become an architect, it seems to confirm the appreciation for aesthetics that she has helped him acquire. When he abandons it to try to make better and easier money selling bonds, it is undoubtedly disappointing to her, but she remains undaunted, continuing to broaden her interests and intellect even in the face of his disapproval and vacuousness.
The indomitability of the human spirit is exemplified by Selina, and the lure of American capitalism by her son, Dirk.