Reviewer's grade: B

A comic-book flick is well-insulated from film criticism. When the movie boasts full-blooded characterization, as is the case with the "Spider-Man" franchise, it earns kudos for ambition. If it serves up eye-popping action, also part of "Spider-Man," it's praised for preserving the spirit of the source material. And when it occasionally stumbles into lazy writing and campiness "” as in "Spider-Man 3" "” some moviegoers are apt to scoff at such protestations and reply: "For crying out loud, it's based on a comic book."

"Spider-Man 3" is great fun for much of its 140-minute running time, loaded with the requisite thrills, special effects and spectacle you expect from summer popcorn fare. But director Sam Raimi lards the proceedings with more plot than the film rightly can sustain.

Trouble mounts for Peter Parker/Spidey (Tobey Maguire), who must fend off challenges from Harry Osborn (James Franco), his onetime pal-turned-Green Goblin Jr.; smarmy photographer-turned-monster Eddie Brock (Topher Grace); and a prison escapee-turned-shape-shifting Sandman (Thomas Haden Church). Even Peter's relationship with Mary Jane (Kirsten Dunst) is on the skids.

That's a lotta story threads for Raimi to weave without entanglement, and the task ultimately proves impossible by the final third, when the film succumbs to contrivance and jarring changes in tone. While "3" falls short of the gold standard set by 2004's "Spider-Man 2," this go-round still offers plenty to satisfy fanboys. PG-13  -Phil Bacharach

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