The book can be summarized as "drink-fuck-drugs-fuck-drugs-drink-fuck-dostupidthings." Towards the end it gets a bit more serious with Mary's suicide and Lauren's pregnancy and subsequent abortion, but the reader is so overwhelmed by the sheer amount of drugs, drinking and meaningless sex by that time, that he hardly can appreciate the gravity.
Ellis uses the expression "Terminally Numb" towards the last third of the book, and that expression by itself describes most of the characters, both male and female, including most of their interactions. At times it seems that there's only one male and one female character, while all the different names seem to be like different moods of the same person. Shawn and Paul and Rupert and Lauren and Mary and Victor and Jaimie, etc.
Ellis seems to be very adept at describing male homosexuality, as almost all male characters in the book are either bi-sexual or homosexual. However, he lacks skill when describing female homosexuality, or female sexuality at all. The one lesbian scene in the book is pretty unconvincing, and the author generally puts much more gusto into describing male sex perception , even if it is masturbation, than female-perceived sex. Mary's pre-suicide thinking is unconvincing, and Lauren comes across as too one-dimensional for what should be the leading female character.
Ultimately, "The Rules of Attraction" is a wishful-thinking, of sorts, for all the debauchery and decadence (and the corresponding price to be paid) that one might have missed during one's undergrad days. Fun, but no cigar.