One can understand why Joseph Gordon-Levitt jumped at the chance to play the crazed, reckless but ultimately soft-hearted psycho who’s the title character in Spencer Susser’s weird coming-of-age drama. Actors love the chance to go all-out, and the role certainly affords it. Gordon-Levitt not only struts, screams, glowers, and delivers a stream of ripe insults for ninety minutes, but gets to turn unlikely savior in the sentimental conclusion. No young actor could resist such a thespian smorgasbord.

Gordon-Levitt clearly relishes everything the part offers. And since he’s one of the most energetic and inventive young actors in the business, you can’t take your eyes off him. Unfortunately, the quality of the material makes you wish you could.

The picture is titled after Hesher, a foul-mouthed, violence-prone slacker who drives about in a decaying old van, but its emotional center is T.J. (Devin Brochu), a young kid trying to deal with the grief of losing his mother in a car crash. He gets little help from his father (Rainn Wilson), who’s gone into a deep depression over the accident, and though his doting grandmother (Piper Laurie), with whom he and his dad now live, attempts to comfort them, she’s so frail herself that her efforts aren’t sufficient compensation. To make matters even worse, T.J. is bullied at school by Dustin (Brendan Hill), an older kid he antagonizes by humiliating him when he goes to retrieve his family’s damaged car at the auto yard where the fellow works—obviously an obsession fostered by his need to maintain a link to his dead mother.

Enter Hesher, who bumps into T.J. and then shows at the kid’s house, moves in uninvited, and pretty much takes over. He’s hardly an ingratiating presence, though T.J.’s father dully accepts his volatility and he and grandma even develop a bond (over some grass, no less). His relationship with the kid, however, remains problematic until the very end. He gets the boy in trouble by handling the bully in his usual reckless fashion, leaving the kid to take the blame; and even when T.J. makes friends with Nicole (Natalie Portman), a kindly grocery worker, Hesher ruins it for him.

But it’s inevitable that Hesher should become a catalyst of redemption for the dysfunctional household he’s taken over, and particularly T.J. And his method of choice is as flamboyant as anything else he’s done through the movie. That makes for an over-the-top conclusion that goes for the jugular and misses precisely because of its outrageousness.

Yet though the script is a manipulative mess and Susser directs it without a trace of style, “Hesher” at least offers a platform for Gordon-Levitt to go for broke—something he obviously enjoys doing. And he’s not its only strength. Brochu makes an appealing young hero, suffering his emotional trauma (and physical exertions) convincingly. Portman, in what seems her hundredth film this year, makes Nicole agreeably perky and persuasively vulnerable, and Laurie dodders with the best of them. As for Wilson, he certainly manages a turn very different from “The Office.”

But all the cast’s efforts are in the service of material that’s decidedly second-rate. Though I’d hate for Hesher to hear that criticism. He’d probably bomb my house.