Chris Columbus, who directed the first two Harry Potter movies, adapts another best-selling novel for young adults: Rick Riordan’s inaugural book about a kid (Logan Lerman) who learns his father is the Greek god Poseidon. Someone has stolen Zeus’s thunderbolt, and Hades (Steve Coogan), suspecting the boy, retaliates by kidnapping his mother (Catherine Keener), which leads to all sorts of mayhem and destruction. The movie feels like a cut-rate Potter knockoff with a dash of Ray Harryhausen: instead of Hogwarts Academy, there’s a forest camp for demigods in training, and instead of a benevolent wizard mentor, there’s Pierce Brosnan trying to look butch as a centaur. The gods, led by Sean Bean, are mostly stiffs; thank heaven for Uma Thurman, raising hell as a stylishly leather-clad Medusa.