What are the main literary themes in While I Was Gone?

The main themes of While I Was Gone are love, selfishness, and obsession. Sue Miller explores these themes through the story of Jo Becker, a wife and mother who becomes interested in a man from her past.
Love is a major theme in the novel. Jo loves her life and husband; she admits that things are perfect. That, however, doesn't keep her from feeling restless and unhappy. While she tries to tell herself that she should be grateful, it doesn't change her feelings. She wants something different, and she's not sure what that is. By the end of the novel, she can recognize that real love is what she has with Daniel, her husband—but by that point, it's almost too late to sustain it, because of her betrayal. Ultimately, though, love prevails, and they're working toward a strong and recovered marriage.
Selfishness is another theme and one that eventually corrupts the Becker family. Jo once left her first husband and lived a life as someone different. Once she reconnects with Eli, one of the men she lived with then, she begins to disconnect from her husband. As she grows increasingly close with Eli, she ignores his insults to her husband and their way of life. Only the revelation that he was responsible for the murder of one of her friends keeps her from sleeping with him.
Obsession is also explored in the novel. The contrast between the obsession that Jo feels for Eli and the love she feels for Daniel is shown by how they treat each other. Obsession runs hot, flares up, and can fade fast. It's new and exciting. The kind of love Jo has in her marriage is steady and unyielding. It isn't exciting, but it does last. The strength of her obsession, though, is so strong that she almost loses Daniel.