Excuse my ignorance, but is the film in any way a spin off from the Batman series?
Yes, it’s a prequel about how the Joker came to be, and why he has animosity toward Bruce Wayne. Without giving anything away, the film gives you insight into what drove the Joker toward violence. It even discloses how he got his name.
Very clever, and very well done.
And PS. I usually do not watch rated R for violence movies, but did watch this one and it really wasn’t that bad.
The Arthur Fleck "Joker" character is not the same Joker who tangles with Batman. The movie takes place when Bruce Wayne is a young child, and Joaquin Phoenix's character is in his 40's.
It's left open as to whether he inspired the later Batman Joker.
It is that Joker but nothing like the Batman series.
Much, much darker.