What is the theme in A Reliable Wife by Robert Goolrick?

Intense sexual drive and acting on that drive, are among the primary driving forces of all three (Truitt, Catherine, Antonio) of the book's central characters. All three want a lot of sex and each reacts differently to their wants. Truitt judges himself all his life and thanks to his mother, considers himself corrupt. Catherine first uses sex as a means of survival, indulges herself in sex, represses her desires in order to get money and security, and then finds those desires released in a surge of passion with Antonio, which she then represses them once again.