Tough. I like The Killing Joke because I like the idea that someone can just snap after a whole day of bad experiences. It feels... normal.
I don't like Zero Year because it portrays Joker as OP right of the bat (lol)
I don't remember what's in The Man Who Laughs and I haven't read the other two

I know what I don't like. An abusive evil aunt who bleaches his face as a kid. I like the art, but the abusive parental figure is so done, even though I appreciate that it's not abusive dad again.