I hadn't heard of We Don't Live Here Anymore before randomly seeing it at Blockbuster, and rented it because I like Naomi Watts and I also like the writer Andre Dubus who wrote the two short stories it's based on. I would recommend seeing it if you want a movie that treats a somewhat disgusting emotional topic with enough black humor and emotional distance that it doesn't exactly hit you upside the head with it.
Jack and Terry are a married couple, as are Hank and Edith. Jack and Hank work together, and all four are good friends. Jack and Edith are having an affair, and we don't even have time to catch our breath before Terry suspects it. Terry, in fact, quickly becomes a very unsympathetic character, despite the fact that she is receiving the most pain in all this betrayal, because we don't even know her being happy before she is merely a frustrated and enraged housewife, and in a strange way that makes us feel even more sorry for her. Just the same, Laura Dern makes her an exhaustingly frazzled presence on screen, and when the film was close to over I just wished we saw more of the other couple, especially since Ruffalo's repetitively agitated performance didn't help the tedium of their arguments. The weakest moments of the film felt like they were trying to imitate the ugliness that was so cleverly prevalent in the dialogue in Closer, but had nothing new to add except for Dern's frenzied jowls.
I think the irony of this film is that the two more intriguing characters are the ones that are in the affair that centers the tension of the story. The scenes showing Jack and Edith in their fooling around are sort of recklessly tender, even though both characters can only bake in veiled self-hatred afterwards. For much of the movie, Jack seems like an unapologetic and despicable man, until we see him with Edith again. We can assume that they love each other, or at least feel more loved with each other, but for the most part the motives behind the affair aren't fully explained. I have to wonder if somebody who's never read Dubus would have a more frustrated response to that; adultery is a consistent theme in his stories, and one that he doesn't seem to hold to romantic relevance. He almost neutrally regards it as something you simply have to realistically assume that an American family is likely to have to deal with at some point, and once there are kids and a house the actual sex part of it is the last thing that should really be an issue. This attitude is reflected in the ending with one couple, but not the other, and for a film that starts off with a rather bad mess, it provides a satisfying enough close.