A canny franchise escapade. It has been excitingly staged by director Sam Raimi, but it’s also a lightweight, mock-campy, script-by-David ”The One-Man Committee” Koepp movie that leaves you hungry for something more. The offbeat casting of Tobey Maguire, with his gurgly-voiced passivity, works well, especially in the early scenes, when sweetly bashful high school science dork Peter Parker discovers his enhanced, super-spider powers. As he learns to control his spurting web (the way adolescents will), he begins to use it as a giant slingshot trapeze, and we’re with him every step — and leap — of the way. The terrific digital effects mirror the crude vitality of the Spidey drawings in the Marvel comics. But unlike, say, Tim Burton’s Batman, the movie never really draws you into an extravagant universe of good and evil at war, and at play.