I've seen this movie described as Hong Kong Zodiac, and while you'll enjoy it if you expect that going in, it really isn't. It's creepy for the same reasons as Zodiac, but Zodiac is a David Fincher movie with David Fincher characters-people who are extremely compotent at their jobs. Memories of Murder is a movie with much more realistic police, mostly bumbling idiots who are completely unable to deal with an actual force of evil. Much like Parasite, its a movie that very clearly describes a problem that leftists see about society, but ia undeservingly sympathetic to its villains in a way that really heightens the movie.

If I had to give a one line pitch for why you should watch it, it's Zodiac with Officer Wiggum.