Tenth of December, George Saunders
I'm not as gung-ho about George Saunders as everyone else seems to be; I didn't love all of the stories in this collection. But "Tenth of December," the final piece (and the one for which the collection is named), is a masterpiece writ small, as many others have already said.
Oddly enough, though, my favorite of his stories in this book was "Sticks." It's quite short, the tale of a man who adorns a metal pole in his yard with holiday-themed decorations: "Super Bowl week the pole was dressed in a jersey ... On Fourth of July the pole was Uncle Sam, on Veterans Day a soldier, on Halloween a ghost." It's a gem, an oddity, and I love how effectively he can sketch the family's life when showing so little of it.