WE'RE NOT GAMBLING ...we're counting," says Kevin Spacey in 21, which is an appropriate way to sum up the film itself. Director Robert Luketic has never once made a movie about actual human beings, and he isn't about to start now, even though he has switched from pinheaded comedies like Win a Date With Tad Hamilton! and Monster-in-Law to a more "serious" drama. And bonus! This one is "based on a true story," which always gives lazy filmmakers carte blanche to let the story glide by on auto-pilot. If anyone balks, they can just say, "But it really happened!" George Washington may have crossed the Delaware, but that yarn doesn't hold water onscreen unless it feels right. And with the soulless Brett Ratner cropping up as one of this film's producers, it's no wonder there's a lack of weight. The good news, however, is that the first two-thirds of 21 has a tantalizing allure, partly because Luketic and screenwriters Peter Steinfeld and Allan Loeb keep us in the dark along with the naive young hero, Ben Campbell (Jim Sturgess). Ben is a superbrain who is about to graduate from MIT. He has been accepted to Harvard Med but lacks the funds to pay for it. A magnificent scholarship lies just out of reach unless he can write a great application essay. Trouble is, he has never done anything worth writing about. Luckily, a math professor, Micky Rosa (Kevin Spacey), notices Ben's steel-trap mind and invites him to join a team of card-counters. The group is made up of the usual two-dimensional character types, plus the cute girl, Jill (Kate Bosworth), Ben has been mooning over; they travel to Las Vegas on weekends and clear many thousands of dollars with their skills.This is where the film gets dopey. Ben promises that he's going to make just enough to pay for Harvard, then get out, but the allure of Vegas and winning and all that goes with it gets to him, and he turns arrogant. The good news is that Luketic's fantasy world of wealth, hotel suites, high-class clubs and expensive clothes rubs off, and it is a lot of fun to give in to it, to luxuriate in it. Spacey's sharp performance, made up of his usual quietly clipped line readings, helps a great deal; he lends the film a sense of cool. In one scene, he insults someone with the words "you arrogant little infant," and you almost wish you could hear him roll those words over his tongue again. Laurence Fishburne turns up as another part of the movie's cool factor; I wish I could say the youngsters had it, but they just don't. Fishburne plays the last of a dying breed; a "loss prevention" agent who takes cheaters down to the basement and pummels them (but only after he carefully removes his ring, slides it around a beautiful pen and pockets both).

Rhis is supposed to be a movie about some of the smartest people in the world, and yet they fall for the oldest, stupidest tricks in the book; the illusion of intelligence is easily shattered. Once the bratty young cast loses that much, they make you yearn for a real cast (George Clooney, Robert De Niro, Sean Connery, Johnny Depp and the like) in a real Vegas movie. Those guys may not be able to count cards, but at least they're not stupid.

21 (PG-13; 123 min.), directed by Robert Luketic, written by Peter Steinfeld and Allan Loeb, based on a book by Ben Mezrich, photographed by Russell Carpenter and starring Jim Sturgess, Kevin Spacey and Kate Bosworth, opens March 28.

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