Paradise and travel
Through the novel, we see the Garden of Eden as a traveling expedition. Although typically, the Biblical motif is invoked as a stationary place that signals innocence and a feeling of home, that isn't true for David. That is insightful, because if David feels most at home when he is traveling, that means that he doesn't really experience any attachment to wherever his real home might be. Travel is delightful, but to feel at peace only when one is traveling is averse and signifies some sort of dysfunction, a dysfunction which the novel elaborates.
The marriage dysfunction
Although David is hesitant, he cannot resist for long when his wife starts offering an affair to him. This relationship between him and Marita is a symbol of the marriage's dysfunction. Put simply, the dysfunction is that the wife doesn't trust the husband, and so instead of being surprised by a covert affair, she is encouraging him to have his affair in front of her, alleging to enjoy it, when in reality, she is just sparing herself from paranoia and disappointment.
The short stories
Through the stories, David is working to write. This is an indication that the book has a quasi-autobiographical flavor, because the writer is writing about a writer writing. Through the short stories, we learn that this author has a hard time seeing to overarching meta-narrative of the stories. As he works to combine the stories into a cohesive novel, he is also striving to perceive himself and his experiences as a cohesive unit.
Alcoholism
The portrait of alcoholism in the novel is both symbolic and literal. It is symbolic, because the slide into addiction is an insightful symbol for the slide into dysfunction and loneliness. The addiction causes mental health issues and also illustrates them in real time. The alcoholism is also a literal portrait of what the disease does; the characters gradually start drinking earlier and earlier, and the chaos of their fully drunken stupors starts creeping into their day earlier and earlier.
Sex and intimacy
Although sex is literally a physically intimate action, the novel exploits sex as a symbol for a lack of intimacy. The wife calls their shared lover Marita, "the spouse of the day," as if to suggest that being a spouse meant nothing at all. Instead of wanting to be intimate with her husband, she wants the intimacy that comes from his honesty; by making him sleep with another partner, she is proving to herself that he doesn't want her in an exclusive way. She is settling for a replacement for real intimacy.
