America is a consumer society, and Hollywood has perfected its rules, manufacturing blockbuster event-films whose narratives are driven by demographic imperatives rather than dramatic imagination.

The studios devise marketing strategies that maximize the subject matter's appeal and work backwards from there. The characters and message of the stories chosen are as carefully tailored to the intended viewers' likes and dislikes as a TV car commercial or a print-media campaign.

Spider-Man, the summer season's first breakaway hit, is a serviceable product. Its distributor, Sony Pictures, has skillfully created a buzz around the film. The result: better-than-anticipated box-office returns. Key to the movie's success is a quick-witted exploitation of recent changes in theatrical releasing patterns.

The good news is that there's nothing to offend family viewers. Good and evil are clearly defined, and you root for the hero to overcome all the obstacles placed in his path. It's an enjoyable roller-coaster ride even though some of the film's pleasures seem at times too calculated. (Parents should be warned that some of the violence in the action sequences may be too intense for kids under 13.)

Spider-Man is an existing franchise with built-in brand-name recognition. Stan Lee and Steve Ditko created the main characters for Marvel Comics 40 years ago and, ever since, its tens of millions of fans have been waiting for the movie version. They won't be disappointed.

Director Sam Raimu (Darkman) and screenwriter David Koepp (Jurassic Park) wisely retain the comic book series' basic premise. It's a coming-of-age story about an ordinary teen-ager who develops super-hero powers but continues to suffer all the agonies of adolescent angst. Young people instantly identify.

Peter Parker (Tobey Maguire) is a senior at Midtown High School in Queens, N.Y. A nerdy outcast who loves science, he is rejected by the school's in-crowd and ignored by the sweet, pretty girl next door, Mary Jane (Kirsten Dunst). His best friend is a fellow loner, Harry Osborn (James Franco), whose millionaire father, Norman (Willem Dafoe), supplies high-tech weaponry to the Pentagon.

Peter is an orphan being raised by his kind-hearted aunt and uncle (Rosemary Harris and Cliff Robertson). They are struggling members of the lower-middle class who instill in him a firm set of moral values.

Peter's life is changed by a field trip to the Columbia University science museum, where he is accidentally bitten by a genetically engineered super-spider. When he wakes up the next morning, he feels different. He discovers he no longer needs his nerdy glasses. His reflexes have developed way beyond those of an ordinary human, and his once-scrawny body has mysteriously grown muscles strong enough to win a weight-lifting contest.

Things suddenly get better at school. Using his new powers, he's able to act out several adolescent fantasies. He rescues Mary Jane from a potentially embarrassing scene in the cafeteria and faces down the class bullies in a hallway fight scene.

But Peter is soon faced with a more important test. His uncle is murdered in a brutal car-jacking and, in wreaking vengeance on the killers, he finds that he can swing from skyscraper to skyscraper in downtown Manhattan, clinging to a web that spews forth from his arms.

Now Peter's moral education begins, and the filmmakers should be credited for underlining its meaning in such an otherwise manipulative marketing product. The superhero realizes that revenge in and of itself isn't satisfying. He remembers his dead uncle's words: “With great power comes great responsibility.”

The rest of the plot follows Peter's progress in learning how to deploy his unique gifts for the service of the greater good, and he turns himself into the scourge of New York City's bad guys, becoming a media star in the process.

Throughout this moral and physical transformation, Peter retains his ordinary, nerd-like personality most of his waking hours. Only at moments of great crisis does he secretly blossom into a superhero with a sleek, spider-like costume to match.

The movie makes the best of this duality just as the original comic did. Mary Jane, of course, admires the celebrated Spider-Man without ever realizing his true identity, and it breaks Peter's heart when she begins dating his buddy, Harry.

Harry's father undergoes a parallel genetic mutation as the result of a lab experiment gone wrong, The slightly shady millionaire is transformed into a malevolent creature with a terrifying mask-like facade who inflicts harm on others for the sheer joy of it. Inevitably, Spider-Man must rise to the occasion and challenge him.

The emotional glue that holds the movie together is Peter's romantic longing for Mary Jane. This is part of a marketing strategy to hook a female audience. The filmmakers cut between it and the thrilling action sequences designed to grab male viewers. This dual gender appeal is modeled on the success of the otherwise very different blockbuster, Titanic.

Thankfully, Spider-Man bucks the currently popular Hollywood trend to frame all moral struggles in relativistic terms. But one risks being a spoil-sport to point out how two-dimensional its depiction of the clash between good and evil seems when compared to The Lord of the Rings' epic treatment of the same theme. This is because Raimu and Koepp are more focused on scratching their audiences' emotional itches than on elevating the human spirit. The result is two hours of consumer fun that leaves no lasting imprint on our consciousness.

John Prizer writes from Los Angeles.