If you’re a Marvel Comics fan, you probably know all about the vexed development history of The Amazing Spider-Man. But if you’re a casual viewer, you may be wondering: Wait a second. Three blockbuster Spider-Man movies were released in the past decade. Why’d they “reboot” the franchise with a new cast, director and storyline, instead of just making a fourth?

Never mind the answer, which has to do with rights, money and scheduling (like everything). The important thing is that casting and storytelling make the difference between superhero movies adults can watch without feeling stupid (The Avengers), and superhero movies that are basically just wish-fulfillment and big blurs of CGI. Directed by Marc Webb, who is known for the above-average romantic comedy (500) Days of Summer, The Amazing Spider-Man has the actors and snappy dialogue it needs, but its story doesn’t stick.

As Peter Parker, British actor Andrew Garfield (who played Mark Zuckerberg’s estranged best friend in The Social Network) does for the character what Robert Downey Jr. did for Tony Stark: He loosens him up and makes him a wild card. That element is vital, given that the movie puts us through the paces of watching an orphaned high schooler dodge bullies, pine after a girl, mess around in a lab and become Spidey-fied all over again.

Some have called Garfield’s performance the “emo” counterpart to Tobey Maguire’s perkier Parker. It’s more accurate to say he does a witty impersonation of a teenager, complete with bad posture, mood swings and random over-application of sarcasm. There’s nothing gee-whiz about this Peter, but also nothing bratty or entitled. When he’s wearing a mask and quipping a criminal into submission, Garfield manages to make this seem like a stunt every nerdy kid would pull if he could climb walls and shoot webs from his wrists.

Comic sparks fly when Peter interacts with his long-suffering aunt and uncle (Sally Field and Martin Sheen); or his love interest, the overachieving Gwen Stacy (Emma Stone); or her prickly cop dad (Denis Leary). Webb slows down and lets these relationships develop believably, with the actors carrying the show.

Where the film goes wrong is in the handling of its villain, Dr. Curt Connors (Rhys Ifans), one of those movie scientists who make the mistake of thinking they can become superhuman by shooting themselves up with nonhuman DNA. (Haven’t they seen The Fly?) Ifans initially comes off as a thoughtful, nuanced antagonist — indeed, scarcely an antagonist at all — but when his transformation shifts into high gear, his human motivations vanish into a cartoony digital monster.

At that point, anything resembling humor or subtlety vanishes, too, and The Amazing Spider-Man becomes — you guessed it — another big CGI blur. Many buildings are scaled, many innocents are saved and many pieces of a metropolis explode so that Peter Parker can become a man. Sam Raimi, who directed the other three films, was adept at orchestrating clever comic-book-style battles, but Webb drops the ball here.

The leerier Hollywood studios become of risking their fortunes on original ideas, the more we’re forced to accept sequels to reboots and reboots of sequels as the order of the day. Like the classic tales that dramatists used to pillage and reshape to their liking, recycled superhero legends can certainly accommodate creativity. But, given the sameness of animation and the international marketability of things going boom, it’s a rare one that doesn’t build to an overblown, forgettable climax. The Amazing Spider-Man starts promisingly, but ends up getting stuck in its own tangled web.