I suggest you keep your expectations low if you’ve read the book. Joe’s backstory and the underdog buildup are both almost nonexistent in the movie, but they are both crucial to the central theme of the tale.
The movie was worth watching, and I realize it would be difficult to fit everything in, but there is just so much missing context. I wonder - if I’d seen the movie before reading the book - if there would have been instances that didn’t make any sense to me.