At first, this appears to be a movie about a family who wants to outdo another Jewish family by having an even more extravagant bar mitzvah party for their son Benjamin.
But when Benjamin secretly invites his estranged hippie grandfather to the bar mitzvah two weeks early, things take an interesting turn. Over the course of the film, Benjamin develops a bond with his grandfather and begins to understand the true meanings of bar mitzvah and manhood and maturity.
So does Benjamin's father. He learns that becoming a Bar Mitzvah (son of the commandment) is not about having a huge party and outdoing the Steins, it's about becoming emotionally and spiritually mature, something that finally begins to happen to him at his own son's bar mitzvah. In a way, the father also becomes a son of the commandment at the same time his son does.
This is one of the better movies I've seen in a while, much more good natured and heartwarming than most Hollywood offerings.