Without realizing it, I had these two movies right next to each other in our Netflix queue, so we watched one bad-marriage movie after another. The Secret Lives of Dentists is based on Jane Smiley's "The Age of Grief," which I read many years ago. We Don't Live Here Anymore is based on Andre Dubus' novella of the same name as well as his "Adultery," in the same volume. I remember trying to read "We Don't Live Here Anymore" once; found it too depressing.
Both movies are well written, and feature great performers and dialogue. While they deal with similar material, they are very different. In "The Secret Lives..." we get the impact of a wife's infidelity from the husband's point of view. His discovery of her affair renders him literally beside himself--he generates an invisible sidekick (based on a troublesome patient) who commiserates over his predicament and challenges him to confront his wife and move on. We get so deep into the husband's head that we even witness his fantasies about his wife's adultery (he doesn't know who she's seeing, so he imagines her with everyone they know, both individually and in combination).
In "We Don't Live..." we see two unhappy couples destroy their marriages. It's an upsetting movie to watch, but ultimately far more satisfying than "The Secret Lives..." because the action happens before us. We don't have to be told about the impact.
"The Secret Lives..." takes place in a space removed from the action--it's all aftermath. When it was over, I wondered, "Who could imagine this was a good idea?" The other movie made me want to try again to read Dubus' novellas.