Sex
The predominant theme of the diaries is sex, primarily because the predominant theme of Nin's life was sex, and the diary is a reflection of her day to day activities and thoughts. Almost every relationship that she has is based around sex. Even her relationship with her father is a sexual one; Anais believes it to be a romantic one, failing to see the inherent incest that it is based upon.
Anais is sexually voracious and however many lovers she has, she is never satisfied. This is most likely due to her father, whose relationship with her has confused sex and love in her mind. Abandoning her when she was a child, he returned and began abusing her; Anais saw this as love and is convinced that she is romantically attracted to her father in the same way that she would be to a lover.
Anais has lovers throughout her marriage, and finds her husband wholly dissatisfying both emotionally and physically. She is also unable to commit for any length of time to any lovers, no matter how obsessed she is with them at the beginning.
Although Anais mentions her work very seldom in the diaries, those novels she does mention have narratives based around disquieting and often downright kinky relationships. Nin is not classified as a sexual deviant but seems to walk the line fairly often, and this is reflected in her writing. She is also attracted physically and cerebrally to writers with similar obsessions; this is why she had such a long affair (by her standards) with Henry Miller. Sex and love, to Anais, are the same thing, and so she writes of sexual encounters with a great many people all whilst trying to satiate her insatiable need for love.
Affairs and Cheating
Unlike most spouses engaged in affairs outside of their marriage, Anais did not go behind her husband's back when cheating on him. In fact, she was always very open, although she did make a pretense of running and errand or doing something else when planning a dalliance. She also cheats on her lovers, again, making no secret of this.
Anais has a way of encouraging married men to cheat on their wives when she wants to have a relationship with them. She befriends both Henry and June Miller, all the while dreaming about, and planning, an affair with Henry which she begins once his wife has left for New York. There seems no shame or guilt on Anais' part when she is involved with a married man; she sees no barriers to her getting the sexual encounters she desires. Affairs are part of normal life in her opinion and almost all of her relationships are conducted in tandem with others.
Incest
Anais is sleeping with her father but seems to have difficulty seeing this as incest. She sees it as a romantic relationship similar to that which she might have with the lovers who have gone before him. Anais is sexually attracted to her father and considers him a lover, not an abuser. She also has a rage against him that she is not entirely sure how to express, and so uses the relationship between them to do so for her. She describes their sexual relationship in great detail, never seeing it for what it is, never mentioning the word incest, and wondering why the rest of the world does not understand the special kind of love that is between them.
