One of the things i'd like to find out from a movie review is if i'll like the movie, but if at all possible, without learning the entire plot with nuances. And that's what is attempted here with Joker.
Let me be clear. There's a pandemic, so i'm not saying you should go out and see this. I'm also not saying you should rent it or stream it. Be safe. But read on to see if you're wasting your time/money.
The 2019 movie, Joker, is an origin story for the (primarily) DC's Batman villain - The Joker. As a comics fan, i'm generally disappointed in movies that do origin stories. As a classic example, Marvel Comic's Spider-Man suffers no less than three quick origin movies, two which are minor changes from the original comics origin, and the third which resets Spider-Man's character who should be about 60 years old now to some time in high school, with no rhyme or reason. That Marvel's characters generally age adds realism to their characters. That Marvel sometimes loses control and by default allows a rehash of the same story repeatedly is disappointing.
The Batman character's story has changed dramatically in various iterations. The 60's TV Batman played by Adam West is a campy show that doesn't take itself too seriously, whereas the Dark Knight gets "why so serious?", from the villain, The Joker. Is this the same Joker as in this 2019 movie? Maybe. That the Dark Knight is so different suggests an excuse for the Batman Begins origin. Fortunately, that movie also has what the new Batman ends up doing, facing a villain, character growth, and so on. Not bad.
You'll like Joker if realism is your thing. And yet, it's easy to imagine that a Joker story could venture into horror, with attendant paranormal activity. But there's none of that here. Joker's insanity is based on real mental conditions. The only horror sort of activity is that it's not at all clear what he's going to do next. In fact, it's not always clear if what has been shown is what the character actually did or what the character imagined. The plot is so good, script is so good, the acting is so good, the photography is so good, the situations are so good, that the result may be a little too close to home for many. Maybe you know someone with a similar diagnosis.
It turns out that i liked it. Here's what i liked about it. With an origin with this kind of depth and realism, it should be easier to write additional excellent stories. It should be easy to add incidents to the base origin that are compatible with the existing story, and hints of these can be added to ongoing encounters with the hero or heros. The hero learns about the character and takes it into account, allowing the hero to be more heroic, and, for example, not simply a guy who spends his nights beating up people with his bare hands. The hero has goals. The villain has goals. They both need to have some complexity if your going to have very many stories with them.