These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Music: Defied. The soundtrack is comprised of the cheesiest 80's songs imaginable and Patrick's tastes are often the subject of parody. Patrick's enthusiasm is oddly infectious, though.
Big Lipped Alligator Moment: In a chapter that begins and ends in mid-sentence, Bateman wanders on the street, doing things like shoplifting a can of ham from Gristede's for absolutely no reason and buying crack rock from a street dealer and eating it in front of him. This just demonstrates his sociopathy; he doesn't feel differently about shoplifting and torturing people to death.
Death of the Author: Explored in Lunar Park. Ellis sees his characters slipping away from him, and the more they get interpreted by his audience, the more he loses control over them.
He Really Can Act: This was the moment everyone started taking Christian Bale seriously as an actor.
Christian Bale plays a wealthy shallow yuppy who never does any work, has a job at his father's company, lives a double life, and is often forced to hide his displeasure at his companions. They have more in common than it seems.
Memetic Mutation: Patrick Bateman (and some of his choice reaction shots) has become memetic in and of himself. Also, the entire Huey Lewis and The News and Phil Collins speeches.
A specific shot of Bateman◊ in that very scene where he is shown pointing towards the stereo has itself became associated with double posts on Image Boards, mostly due to his general pointing direction ends up pointing towards the post number. He has been nicknamed the "Doubles Guy".
What Do You Mean, It's Not Political?: A major theme underlying the film is that the less violent aspects of Bateman's sociopathy are much in line with the prevailing right-wing philosophies of The Eighties. Of particular note is his insane homophobia, and the several conversations he and his associates have about how they believe that a straight man can't get AIDS (during the Reagan administration, the government did almost nothing to inform the public about AIDS). Bateman himself also makes several references to Reagan, and how Bateman believes he is just as insincere as Bateman himself. He also enjoys taunting the homeless (when he isn't killing them) by calling them deadbeats and spouting Reagan-esque "wisdom" at them.
There's also Bateman's little speech towards the beginning of both the movie and the book, where he mentions all the "hot button" topics of the '80s, mention how "we need to do this, do that, do this, etc"... while completely failing to even begin explaining how he plans on fixing said problems, mirroring the "feel good" politics of the '80s that pumped up confidence in America while failing to solve any real problems.
Bateman and his circle of "friends" are also extremely shallow, and are completely obsessed with having everything that everyone else they know has, but bigger, better, more expensive, representing the vapidity of '80s consumer culture.
What Do You Mean, It Wasn't Made on Drugs?: Rambling sections of this book delve into this realm, including a chapter that switches to third person partway through, only to switch back to first towards the end of the chapter.
Remember that it's all supposed to be Bateman's own firsthand accounts, so if anything, this is more like "What Do You Mean the Narrator Character Isn't On Drugs". Which, in the story, he very frequently is.
In the movie, there's only a few instances of Bateman using drugs. He does take some pills before he kills Paul Allen, and there is one point when he's snorting coke, although he discovers that it's half a milligram of sweetener (or very, very cut). Timothy Bryce is notably taking a number of drugs, although many of the scenes that emphasized this character trait were deleted from the final cut. And, of course, Courtney Rawlinson is normally operating on one or more.
That being said, Ellis has made little secret of his problems with drugs and alcohol, so this may well be a literal example of the trope.
The Woobie: Jean. Bateman offhandedly insults her outfits several times, and she was obviously waiting for that date with him for years. The date ends sourly. Also, in the film, she finds his journal with images of murdering/raping women.
A scene in the book involves Jean's hesitatant admission of love to Bateman. His response is even more tentative because he is unable to explain to her the sheer extent of his sociopathy and depersonalization. This frames just how hopeless her love for him is; Bateman even points this out in his own internal monologue.