The subject matter of Steven Dietz's wonderful new comedy—long-term marriage, midlife stasis, cars—could hardly be more middlebrow. But out of these mundane bits Dietz spins a rich, surprising, emotionally gratifying tale that'll crack your shit up (and should get Dietz on the Pulitzer short list). Aiding things immeasurably: an exemplary cast led by the brilliant Kimberly King and Charles Leggett, who, among many other accomplishments, create one of the most realistic families you'll ever see onstage. (ACT Theatre, 700 Union St, 292-7676. 2 pm, $40. Through Nov 16.)