If you've seen the ads and trailers for this movie, then you're probably expecting a wistful romantic comedy about a sad woman who learns to connect with others -- and maybe even finds love -- after the death of her beloved dog. You have been wildly misled.
That's how the movie starts off, to be sure. When we meet Peggy Spade (Molly Shannon), she's living alone with her beagle, Pencil, and seems to have only one friend in the world, co-worker Layla (Regina King, playing the Sassy Black Chick in heavy-handed fashion). Her brother and sister-in-law live nearby (Thomas McCarthy and Laura Dern, who is quite funny as an obsessively concerned mother), but even those relationships aren't as important to Peggy as Pencil.
When Pencil dies, Peggy does meet a couple of men -- her neighbor, Al (John C. Reilly), and Newt (Peter Sarsgaard, the warmest and most likable person in the movie), who works at the dog pound. But neither of them works out romantically, and the movie becomes the story of Peggy's increasing involvement with animal rights issues, an involvement that rapidly crosses the line from simple political crusade to dangerous obsession.
The last half of the movie is relentlessly bleak and gloomy as Peggy slowly loses her grip on reality; it would be bad enough if she were only ruining her own life, but her obsession is causing problems for everyone else, too, and I began to wonder why her friends and family didn't simply have the poor woman institutionalized.
Molly Shannon is at her best in the first half of the movie, when things are still relatively light and comic, but she's not a good enough actress to pull off the shift into darkness in the second half of the movie. Dern, Reilly, and Sarsgaard are almost good enough to salvage things, but the movie ultimately collapses around Shannon's limitations.
The kindest thing I might say about Year of the Dog is that it's an interesting failure. If you feel you must see it, I'd wait for cable or DVD; there's certainly nothing of visual interest that would require you to see it on the big screen.