In Dinner at the Homesick Restaurant, the main issue is family. Pearl and Buck have children together, yet they do not succeed as a family. Buck feels no obligation to continue living with someone merely because they have children together. Pearl is so obsessed with her misery that she cannot see how it is corrupting the life of her family. Jenny, Cody, and Ezra may start out as children, but eventually take on the components of family among themselves. Buck has a child whose mother never felt the need to tell him about his paternity, because it takes more than a sperm donation to make a father.
In Atonement, the main issue is one's perspective on life. Briony's ignorance of her sister's situation colored her perception. That in turn led to a series of unfortunate circumstances, as being unenlightened continued to prevail. Even the truth could not set Briony free. Her only path to atonement was to fade into a world of fantasy.