American Fable is ambitious, maybe too much so sometimes, but there's an intense pleasure in the boldness of the film's style.
Every movie involving superheroes requires an origin story, and "Percy Jackson & The Olympians: The Lightning Thief" has a doozy. The Greek gods on Mount Olympus sometimes descend to earth to have children, you see, and these half god, half humans are demigods. They live among us. One is Percy Jackson (Logan Lerman), who is the teenage son of Poseidon and Sally Jackson (Catherine Keener). But he doesn't know this. I wonder if his mom noticed. Kind of a letdown to discover Greek gods are runaway dads.
Percy finds he can think best when underwater for 10 minutes at a time. Poseidon was the god of the sea, you will recall. His best buddy is Grover (Brandon T. Jackson), who is revealed as a sort of assistant demigod assigned to watch over him. His teacher is Mr. Brunner (Pierce Brosnan), who is actually Chiron, a centaur. Give Brosnan a lot credit for wearing the back half of a horse as if he'd been doing it for years.
The movie, based on a novel by Rick Riordan, has fun working out modern parallels for Greek mythology. Percy, for example, thinks he is dyslexic, but it's only that his eyes instinctively turn English into Greek letters. That's no help in class. After learning of his real identity, he goes off to Chiron's demigod training camp with Grover, and he becomes friends with Annabeth (Alexandra Daddario), a demi-goddess if ever I've seen one.
The plot heats up. Zeus (Sean Bean) and Poseidon (Kevin McKidd) meet atop the Empire State Building to discuss Zeus' missing lightning bolt, which he believes Percy, Poseidon's son, has stolen. (The story requires a certain suspension of disbelief.) Why, when or how he allegedly might have done so begins as a mystery to Percy, but eventually the situation leads to slam-bam special-effects sequences, as the gods and demigods do battle.