A hippieish college student, finishing up a cross-country bike trip, arrives to stay with his 91-year-old grandmother in New York City. They form a bond, and family secrets are revealed. In outline, Amy Herzog’s play seems like nothing special. But her humor, honesty and narrative subtlety make this a rarity: a family play that avoids sentimentality or sitcom shtick. Daniel Aukin’s production, which had an all-too-brief run at Lincoln Center in the spring, could not be bettered, especially with Mary Louise Wilson as the cantankerous grandma. She creates one of the most poignant, least patronizing portrayals of old age I’ve seen onstage.