The link posted is of an article which looks back at Less than Zero. As the sequel was published, there seemed to have been a rise in interest of the first novel, maybe to refresh people's memories before going on to the sequel.
The author of the article discusses the downward spiral that is experience throughout the book. Indeed, Clay, and his friends, experience events which go from bad to worse, culminating at the scene of the rape. He also discusses the loss of interest the characters experience, in themselves as well as in others.
Clay drives aimlessly through LA, does not care where he is going, why he is going; only point is to drive. He is incapable of finding anything that makes him happy and wants to be as detached as possible.
All of this highlights the feelings that the 80s teen generation must have felt. Obviously not everyone, but the crowd that goes from party to party, takes drugs, drinks excessively. There was a certain numbness that went with the lifestyle. Evidently the drugs and the alcohol made you numb to society, to reality. But it slowly took you away from your own self as well. The 80s youth that is depicted in Less than Zero is a youth that has lost interest and that is escaping from reality as much as it can.
Clay does recognize that he has a problem and finally decides to leave LA. By doing such a thing, Ellis is linking LA to all of the vices, the drugs, the alcohol, all of the bad things. And hopefully by leaving such an excessive city, Clay has a chance to a normal life, or at least, he can escape far from all the problems and try to reflect on them.