Odds are you're going to like this lively spin on the true story of six MIT mathletes who broke the Vegas bank in the 1990s. Loosely adapted from Ben Mezrich's best-selling Bringing Down the House, the movie stretches facts like taffy but never shirks its responsibility to entertain. And, jeez, it's a kick to see Kevin Spacey up to his old tricks as the sultan of snark. Spacey plays Mickey Rosa, a math prof who cherry-picks the brainiest students to join his secret club of card counters. They rake it in at blackjack on weekend trips to Vegas. His newest recruit is Ben Campbell (Jim Sturgess), an innocent with a knack for numbers to rival Rain Man's. Sturgess does a nifty job as this poor Boston lad, given that he's a Brit best known for starring in Across the Universe. The guy has acting chops and a built-in appeal that keeps us in his corner. It's a good thing, since Ben, who needs $300,000 for tuition at Harvard Medical, does some pretty stupid things to get it, like signing on with Mickey against his better instincts. And with Kate Bosworth slinking around as Jill, one of Mickey's spotters, he's a goner. Director Robert Luketic (Legally Blonde, Monster-in-Law) would like to be Scorsese following the money during the first third of Casino. He's not. But the setup for the sting is irresistible. Ben and the experienced Fisher (Jacob Pitts) do the heavy betting while Jill, Choi (Aaron Yoo) and Kianna (Liza Lapira) do the spotting for hot decks and the appearance of Cole Williams (a glowering Laurence Fishburne), the casino head-basher who steps in — there's no law against card-counting — when the house loses. 21 drags itself to a climax that puts credulity in splints. So what? In a multiplex of dumb-luck hits, it's a kick to watch Spacey and a gifted young cast use smarts to deal audiences a winning hand.