Dramatic feature films about card-playing are extraordinarily tough to pull off. Be it 1998's "Rounders" or 2007's "Lucky You," recent attempts at this sub-genre have largely left audiences cold. What may be tense or exciting for the person playing the game isn't nearly as diverting for the viewer sitting in the theater watching a bunch of cards being dealt. And, if this form of entertainment does strike one's fancy, there are plenty of television programs on the subject to satiate anyone's appetite. "21," however, gets it right, using the potentially get-rich-quick scheme of expert card-counting as a means of telling a provocative human story of a bright, financially strapped college kid who, at least for a time, loses himself as he gets sucked into a world of late nights, high stakes and fast cash.

Ben Campbell (Jim Sturgess) is a just-turned-twenty-one-year-old senior at Boston's M.I.T. He has a 4.0 GPA and the talent to go far, but all the intelligence in the world isn't necessarily going to buy him a scholarship to Harvard Medical School, which costs far more money than he has. Enter mathematics professor Mickey Rosa (Kevin Spacey), who sees undeniable potential in Ben's skills and invites him to join his under-wraps card-counting business, made up of fellow students Jill Taylor (Kate Bosworth), Choi (Aaron Yoo), Kianna (Liza Lapira) and Fisher (Jacob Pitts). Ben reluctantly accepts the offer, insisting that his intentions are only to earn the $300,000 needed for med school, but as his skills broaden, his loot deepens and the group's secret game-playing codes become a second language—each number is assigned a word, and vice versa—the weekend high life in Las Vegas starts to take precedence over the more honest goals and ambitions he once had set for himself. And, when a reckless action puts him in direct defiance of Mickey's teachings and instructions, he suddenly faces losing everything he has worked for.

Director Robert Luketic has helmed a number of high-profile motion pictures—2001's "Legally Blonde," 2004's "Win a Date with Tad Hamilton!" and 2005's "Monster-in-Law"—but all of the above have been lightweight comedies in the same basic realm. With "21," Luketic has drifted out of his comfort zone and made a movie that is altogether more serious, mature and involving. He proves his capabilities and exhibits range, certainly, and yet he stays true to himself as a filmmaker. Despite the story being realer and darker, Luketic does not lose his sense of fun. If "21" is only one thing, it's intoxicating. The glittering neon lights, boisterous energy and pulse-pounding anything-goes nature of Las Vegas has rarely ever been captured on film with this much sexiness and exultation, and the pure exhilaration that Ben experiences in his discovery of Sin City carries over to the viewer. Cinematographer Russell Carpenter (2007's "Awake") has outdone himself in bringing Vegas—and, for that matter, also Boston—to palpable life.

Based on the non-fiction book "Bringing Down the House: The Inside Story of Six M.I.T. Students Who Took Vegas for Millions" by Ben Mezrich, "21" isn't clear about the complex details that go into card-counting, but screenwriters Peter Steinfeld (2005's "Be Cool") and Allan Loeb (2007's "Things We Lost in the Fire") do a fine job all the same in touching upon the tricks of the trade so that one can easily follow what is going on at the Black Jack tables. Where the film really succeeds, though, is in the character study of Ben Campbell, an upstanding young man of solid values who is wheeled and dealed by Vegas just as much as he pulls one over on the casinos. Recognizing too late the seduction that money and power have over him, Ben's newfound cockiness gets the best of him, and no one—not his snubbed, decidedly nerdy old buddies back at school, and not new girlfriend Jill Taylor—is able to get through to him before he is faced with a bitter wake-up call.

Sporting an uncanny American accent, the British-born Jim Sturgess (2007's "Across the Universe") is outstanding as Ben Campbell, a protagonist who, if written with less depth and played by a less likable actor, could have come off as insufferable. Instead, Sturgess admirably ignites Ben with the character shades necessary to care about him at the onset, understand him even when he changes for the worse, and ultimately root for him to find his way back to a straight and narrow path. This would be an uncommonly rich part for any young up-and-coming actor, and Sturgess runs with it and makes it his own.

As love interest Jill, Kate Bosworth (2006's "Superman Returns") is confident without seeming unattainable, and brings a down-to-earth quality to the role. As Professor Mickey Rosa, Kevin Spacey (2007's "Fred Claus") is a tough-as-nails force to be reckoned who at one point makes it very clear to Ben that they are not friends, but business associates. Aaron Yoo (2007's "Disturbia") and Liza Lapira (2008's "Cloverfield") are charismatic presences as card-counting coconspirators Choi and Kianna, but have significantly less to do, while newcomer Josh Gad threatens to overdo it as Ben's former best friend Miles, whose unkempt dorkiness is too on the nose.

"21" is a pulse-poundingly high-spirited and extremely well-directed drama that feels like one, long getaway to Las Vegas, fraught with untradable fond memories and a threat of danger lurking at its underbelly. With the pace never ebbing, the superbly chosen soundtrack always pumping, and Ben serving as the viewer's continuous tour guide, the film is an enthralling mix of frivolity and morality tale. The third act, which features a plausibly sly twist followed by an emotionally satisfying wrap-up, surpasses expectations. "21" is a welcome respite in that it is smart, thoughtful and genuinely potent as entertainment, three adjectives that do not usually go together in a Hollywood production involving college-aged characters.