I generally avoid violent films...which is why I resisted watching "Casino" for a long time. However, despite being very violent in spots, the film turned out to be very compelling....it was far more than just violence and had an interesting look at the mob influence in Las Vegas back in the day.
The film is unusual in that it has two leading men with parallel stories. Sometimes Ace and Nicky (Robert De Niro and Joe Pesci) were in scenes together....often they were apart...each doing his own thing. As for Ace, he was a smart man who was in charge of one of Vegas' top casinos. He was tough...but basically honest for a mobster. As for Nicky, as you'd expect with a Joe Pesci character, he's a bit of a nut-job....often out of control and letting anger govern most of his decisions. Unlike Ace who had a veneer of honesty about him, Nicky was a hood...and didn't mind this. Eventually, the pair end up having a downfall. How and what happens to each you'll have to see for yourself.
The parts of this film I enjoyed the most were when you learned about how Vegas operated. Seeing Ace dealing with crooked gamblers was especially interesting. And, in this sense, I enjoyed the film much more than "Goodfellas"...also with the same stars and same director. This is because "Goodfellas" was mostly just about violence and crime...whereas "Casino" seemed to have more story and wasn't always about excessive violence and nastiness...not that the film is in any way a 'nice' picture. It's filled with obscenities, nasty folks and a few scenes of horrific violence. Think about this before you decide whether or not to see the movie.
By the way, this is only a personal choice and doesn't really affect the movie much, but one thing I did not love about the film is the omnipresent pop music....which at times made the film seem like a music video. I think less of this would have been nice.