I don't think the storyline sounds much - a killer gets out of prison and full of remorse, tries to make amends with his victim's family. The acting and and a creative set of sub-plots make this into a far better movie than expected.
It works because of some great characters. You feel little for Billy Bob Thornton (the killer) as he bumbles through the plot making few decisions, this is intentional. Holly Hunter is great as the brother of the dead man and far more foxy than I expected of her. Morgan Freeman, and Kirsten Dunst bring great angles to their flawed but likeable characters.
These four actors (Dunst, Freeman, Hunter, Thornton) and some great writing and directing turn this basic plot into what ends up as a very good film. It is believable and involving, and the simple story line is not a limitation, but more of a starting point from which characters and sub plots develop.
Unusually the incidental music brings a lot of tension and confusion in the right places; I've never felt this aspect to be notable in a film before.
The plot isn't particularly inventive, but fairly warming and enjoyable. The screenplay and acting lift it far above that. Good film and very much recommended.