American Psycho is the modern equivalent of The Great Gatsby, where money is king and shallow appearances are the only thing that matter. Where Gatsby focuses on the American Jazz era, Psycho is the Yuppie (Young, Upwardly-mobile Professional) decade of the 1980s, set in Wall Street, New York, at the time of the great economic boom.
The first half of the book demonstrates, in great tedious detail, the superficial lifestyle of the wealthy. Every character in every scene is described by their designer clothes, from their sunglasses to their underwear and socks; grooming and television rituals; where and what they eat in expensive trendy restaurants and hotels; their crass and vacuous conversations about other rich people and how to match handkerchiefs and socks.
However, underneath this frivolity is a very dark and disturbing theme. There is plenty of wealth but no value. Racism is cruelly obvious as the homeless and low-paid workers are not part of the Yuppie elite and are ridiculed, mutilated and murdered for no other reason than that. The grotesque objectification of women is taken to the level where they are literally bought and treated as things to be used and discarded in obscene scenes of depravity and horror.
The protagonist talks about how he would like to murder, or has murdered or tortured people, but none of his peers listens or takes him seriously. There are frequent cases of mistaken identity or name confusion. Characters swap partners as there are no emotional bonds. None of this matters because everyone is the same and therefore interchangeable.
As the story develops, the violence, obscenity and murder increase. Sometimes the protagonist feels as if he is a film, another superficial and fake version of reality, and he refers to himself in the third person with exciting action scenes typical of Hollywood. He is not sure what has taken place is in his head or not and tests his peers about missing persons he believes he has murdered. He obviously thinks the ramifications would be more satisfying or at least acknowledged.
This is very much an anti-materialistic tale. These characters have everything money can buy, but they are empty and hollow inside, devoid of love, compassion and fulfilment. Perhaps torture and murder is a way to connect with the living and life because the designer clothes and gadgets don't fill the hole. What is missing is a heart, something the American Psycho, the consumerist capitalist, does not have.