When I first saw this about 5 years ago I really had no idea what to expect. I hadn't, and still haven't, read the comic on which its based and went to see it cold based on my love for Cronenberg and Mortenson's work. I believe that there were some major changes made to the original story though, so that could be a factor in why any fans of the comic might have have a problem with the film.
Taken at face value the plot is very simple. Tom Stall(Mortenson) runs a coffee shop in a quite, peaceful town in Indiana. He has a loving wife(Maria Bello) and kids and is pretty much living "the good life". One day two vicious criminals(introduced at the beginning of the film) walk into his diner to hold up the place. When they make it clear that they intend to kill a waitress, Stall fairly deftly disarms and kills both men. He is hailed as the town hero, but this brings unwanted attention from Carl Fogarty(Ed Harris) and his men who confront Stall, convinced that he is someone from their past named Joey Cusack. Stall denies it, but as it becomes clear that Fogarty is not going away, cracks begin to form in Stall's psyche and in his close knit family unit.

Just in case you haven't seen this, I'll stop there. But really, that is the bones of the story. This is more about the character. And what a character Tom Stall is. David Cronenberg is a director fascinated by duality that can exist in people and definitely seems drawn to projects that highlight that.
The Fly, Dead Ringers, Crash etc are all extreme examples of characters being taken over by their darker sides in a way. A History Of Violence is no different, but whereas much of his earlier work involves a sci fi element as man sometimes literally bonds with another organism or a machine, here it all happens in the very real world of Stall's repressed personality. The changes that come over Stall, as well as his wife Edie and their entire world basically, are handled expertly and even when things seem to get a little far fetched we are never once taken out of the film. Unfortunately, some of the other elements are not handled as well. Early on there are big script howlers. At one point Tom's son Jack(Ashton Holmes) looks out the window at some reporters gathered to interview Tom after the diner incident and says "Dad, look, they are all here to talk to you because of what you did". Yeah, no shit kid. How that one made it past the first draft I will never know! Its just one example. Basically the entire sub-plot involving Jack and some very cheesy, archetypical school bullies feels like it belongs ion a different film. It might sound like I'm nit picking a bit but its only because the rest of the film is so good that these parts stand out as being sub par.
And the major reason behind the overall quality on display here is without a doubt Viggo Mortenson. He is always at the very least good, but at times he really impresses. He convinces completely in what is really a dual role. The transformation that creeps over Stall is at first quite subtle(aside from the bouts of extreme violence of course), until, when he accepts that he has no choice but to become Joey Cusack again and the changes are physical, and vocal. Many actors would have blown this and resorted to hamming it up, not Mortenson. Its pretty much a pitch perfect performance. Bello also shines as Edie, who undergoes her own transformation in many ways. There are two fairly graphic sex scenes in the film, both instigated by Edie, both very different and for very different reasons. In essence, she is having sex with two different men after all. Bello had to be every bit as convincing as Mortenson for their relationship(which is the basis for the film) to work and she is. Ed Harris is as good as ever playing the bad guy, although I would have liked it if he stuck around a bit more. And an Oscar nominated William Hurt pops up briefly at the end and DOES ham it up, but in a good way! The only stumbling block performance wise is Holmes as Jack. Like I said he is not helped by the script at times, and isn't bad. Some of his scenes just fall a bit flat.
The ending of this movie has divided opinion a little. I loved it. I actually can't think of a better final shot. Can Tom really lay Joey to rest again and lead a normal life? Should he even be allowed to? Its very interesting that although Tom Stall is the hero of the story, he was(is?) also an evil bastard. Cusack wasn't some good natured gangster that went along with a life of crime like say Ray Liotta's character in
Goodfellas. He was a sadistic, ruthless killer. Think Joe Pesci! Maybe this film asks the question: No matter how bad a person was, if they really repent and want to change their life should they get a second chance? Or maybe the title doesn't just refer to Stall's past, but to human nature in general. Will we always be predisposed to solve our issues with violence? I dunno, its all there if you want to look, but if you just want to watch a great thriller in which Viggo stamps on a dudes throat repeatedly then it works on that level too!
Be sure to check it out if you haven't already. Also
Eastern Promises for another great Croneberg/Mortenson team up.