He did obviously plan the murder ahead, seeing as the room is covered in newspapers and plastic. But the theme of Bateman’s vanity and cluelessness runs throughout the film and especially, much more so, the novel.

Bateman later goes to Allen’s apartment, iirc to make it look like Allen went away on a trip. The book has this passage, that afaik didn’t make it to the film: “I have a mild panic attack seeing that Allen’s apartment is nicer than mine.”

You know how he occasionally cites the brands of clothes he’s wearing, or whatever else? The novel is pretty much half endless brand-dropping, interspersed with the gore. After a while on that merry-go-round, the reader is equally nauseous from both.

Funny thing, someone once noted in a discussion like this, that if the reader actually knows eighties’ fashion brands, it’s clear that all the VPs in the book dress like clowns. Specifically, if it was reflected in the film, all of them would look like Luis Carruthers (the gay guy).