By Adam Markovitz
Updated February 12, 2010 at 05:00 AM EST

For those who haven’t read the hit Percy Jackson books, here’s a crib sheet for that humdinger of a title: Teenage Percy (Lerman) discovers he’s actually a powerful demigod; the Olympians are the feisty deities of Greek mythology (including Percy’s absentee dad, Poseidon); and the lightning thief is the unknown bandit who has stolen Zeus’ thunderbolt, dooming the entire world — unless young Percy can find it. Punctuated by painful dialogue and high-camp celeb cameos (notably Uma Thurman as a vampy Medusa), the ensuing quest has all the CGI sorcery of a Harry Potter pic, but none of the magic. C+

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