The weak womanizer
Rob is a selfish womanizer who projects a confident front that helps him to get girls, but then he cheats on them and misuses their attention. He is a person who struggles to connect emotionally with women because he suffered a past rejection that left his self-esteem low and shattered his emotional relationship to self. Therefore, he attempts to bolster his self-esteem by rejecting others. The mark of this irony is that Rob inflicts the wounds that were inflicted on him, instead of learning empathy.
Self-sabotage
Rob wants to be happy, right? That is a complex question. It seems that he wants to be happy, but then again, he clearly self-sabotages throughout the book. When his relationships seem to be going well, he gets paranoid that she will leave him, so he ruins the relationship before she gets the chance. The case for this (although there are others) is Laura, who he cheats on. His insecurity is constantly worsened by his own tendencies to self-destruct.
Preference and love
Whenever Rob ranks women, he is demonstrating his point of view about people. Clearly, he sees women in a rank—some are more "worthy" than others. This is ironic, because this is his attempt to establish himself as a worthy person, but if he stopped judging so capriciously and preferentially, he would see that one shouldn't objectify people this way. Perhaps this discovery could heal him of his fear of worthlessness. When he realizes through epiphanic revelation what love really looks like, he sees that he has been holding other people down to lift himself up, like a person who can't swim trying not to drown.
The death of Laura's father
If he doesn't love these women, then why does Rob care so much when Laura's father dies? The answer is complicated. Firstly, death is an ironic part of life, not because humans don't know about it, but because society shrouds it in politeness (dramatic irony), and the death reveals that hidden truth, that human life is not eternal. He realizes that he wants to be married, he had better figure his issues out. There is also the other dramatic irony, that secretly, he longs for a love that is deeper than the erotic love of his spouse. The father's acceptance was an offer of family love. He realizes he wants to be established in the respect of a family.
Commitment as a boon
At the beginning of the story, nothing seems less appetizing to Rob than commitment, but the very path he avoids most was the path he needed. He learns to see commitment as a blessing through the story, and when Laura finally accepts his approaches, he seizes the opportunity. He realizes that commitment was what he longed for all along, but he was confused by self-esteem issues that made him hesitant and unsure. Once he sees the darkness of death and loneliness, he is oriented to hold commitment as a top priority.
