"(500) Days of Summer" is a breezy first feature by former music-video director Marc Webb, and it looks nothing like what you'd dread: It's light and airy and filled with surprises. The picture was written by two hot up-and-comers, Scott Neustadter and Michael H. Weber, who clearly know more about life than what's taught in screenwriting courses. And while what they've created is a love story, it's a love story of an unusual sort. As a voiceover tells us at the beginning of the film, "This is not a love story."

The picture could be pigeonholed as a romantic comedy, but it's not about finding the right person — it's about finding the wrong one. It's also about the pitfalls of euphoric infatuation: how it misguides us, while at the same time driving away the object of our desire, who, inexplicably, doesn't share our heart-bursting love jones.

The two leads, Zooey Deschanel and Joseph Gordon-Levitt, are an ideal match — they have the perfect chemistry for a tale in which the chemistry between their characters has to be just a little off. He plays Tom, an architecture student who after school drifted into a job as a crafter of platitudes at a Los Angeles greeting-card company and has never moved on. She's Summer, the new girl in the office. The other guys in the shop all take their shot at her (and reassure themselves when she doesn't respond that she must be a lesbian or something). Then one day when Tom's in an elevator, listening to some music on his iPod, Summer steps in. She hears the buzz leaking out from his headphones, taps him on the arm and says, "I love the Smiths." Then she gets off. Ka-boom — Tom has suddenly found his dream girl. Or, as he soon puts it, "I know she's the only person in the entire universe who can make me happy." Uh oh.

The writers keep the story hopping by telling Tom and Summer's story out of sequence, as a sort of Cubist narrative. The movie begins at "Day 290," and then skips around to "Day 4," "Day 321," and so forth. At the outset, Summer acknowledges Tom's interest but is upfront about where she's coming from. She thinks love is a fantasy, a delusion. "I'm not really looking for anything serious," she says. "Is that OK?" Their relationship doesn't blossom, exactly, but it evolves. There's a kiss in the copy room, a tipsy karaoke night, a hand-holding romp through an Ikea showroom (very funny), and — finally — sex. In fact, shower sex. As far as Tom's concerned, this is the real deal — he and Summer are a couple. She declines to put a name on whatever it is they're doing, though. "Who cares?" she says. "I'm happy. Aren't you happy?"

Of course not. He's miserable. The girl of his dreams remains, maddeningly, just out of reach. He can't possess her. A buddy tries to help, talking about his own longtime girlfriend: She's "better than the girl of my dreams," he says. "She's real." Tom's not listening.

Zooey Deschanel's searchlight eyes have never been bigger and bluer than they are here, and we understand why Tom would be instantly smitten. But she's a subtle comic actress, and her performance as Summer — maneuvering around Tom's romantic effusions without coming right out and hurting his feelings — is a remarkable balancing act. And Gordon-Levitt — a born leading man — deploys his trademark tousled charm very shrewdly: His Tom isn't stupid, he's just blind. Who hasn't been here?

We keep hoping things will go right for these two — aren't they perfect for each other? But slowly we begin to suspect that they might not. Any shameless rom-com director would slap a happy ending on this picture and ship it off to chickville. Webb and his writers have more interesting things in mind. We keep hoping, though — couldn't there be some sort of romantic salvation at the end? Well, sort of. Maybe.

Don't miss Kurt Loder's review of "Harry Potter and the Half-Blood Prince," also new in theaters this week. Check out everything we've got on "(500) Days of Summer."

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