Paradisal imagery
The novel's title makes the reader consider this imagery before they open the book for the first time. The paradisal imagery of the Garden of Eden is actually not a stationary experience of home at all. Rather, paradise is shown to be travel and new adventures. But, just as the Bible's Eden is temporary and fleeting, Hemingway's paradise of travel and beauty is also fleeting. Without stability and the daily involvement in a role, their never-ending vacation starts to become a hell.
Marriage and dysfunction
The marriage is strained by distance and distrust. The wife feels that the husband is withdrawn, and so she assumes that he must not like her that much. She invites a partner for him to play with, and although David believes one thing about this, the reader knows that it is a concrete use of imagery. The imagery exposes the dysfunction of the relationship; although she wants intimacy, the wife is happy to accept pain and honesty. Her aversion to paranoia makes her crave control, and so she decides if he might cheat, she'd rather it be in a way she can see and control.
Writing and artistry
The truth about the husband's detachment is shown to be his involvement in his art. The way he participates in his art has concrete and abstract qualities. The concrete tasks of his daily life are proof of this imagery, but more interesting is the abstract quality of his attachment; both women strive to ingratiate themselves into the book, hoping to be helpful to him, often calling the book "theirs" instead of "his." The love the author has for his book makes his wife jealous (which is basically the point of the book; Hemingway is telling us about his own strained marriage).
Loneliness and mental health
Although the book is about intimacy on its face, since the novel chronicles various sexual escapades, the mental health crisis the plot evokes is unignorable. The loneliness starts on the first page and continues. Alcohol is an important part of this dynamic; as the menage-a-trois goes on in their paradise, the drinks begin earlier and earlier, and the loneliness of their dysfunction becomes more and more clear, until they are at crisis.
