There is a sense in which this novel has more to do with sex than with love, but I believe we can usefully explore the theme of love through examining the role of family in the novel and the way that it shows how characters who are part of the same family love each other and express that love. This is most clearly seen through the way in which the character of David Lurie moves from being a rather selfish and egotistical individual who only cares about himself and his own gratification to rediscovering his role as father.
Note how the following quote describes Lurie's relationship with Lucy, his daughter:
From the day his daughter was born he has felt for her nothing but the most spontaneous, most unstinting love. Impossible she has been unaware of it.
As he moves to the farm in rural South Africa where Lucy lives and works, David comes to learn once more how to coexist with his daughter and to also accept her as an adult, exploring how his role of father must change as a result. Love therefore is something that is most usefully expolored through the context fo familial relations and can be seen not only in this central relaionship but also the way in which Pollux is protected and shielded by Petrus and how Mr. Isaacs angrily confronts David about his relationship with his daughter. In a sense, this presentation of love acts as an antitode to the emphasis placed on sex in this novel, which is largely self-serving. The familial love represents a more ideal and self-sacrificial emotion.