Dating back to 17th century France, blackjack is a deceptively simple game of luck and skill that remains a firm favourite with gamblers.

The rules are simple: take successive hits from the deck, against other players and the dealer, to accumulate the highest scoring hand without exceeding 21 points.

Naturally, the odds are stacked heavily in favour of the house... unless you attempt to count cards to assess the likely probability of drawing a winning hand.

Adapted from Ben Mezrich's fascinating book Bringing Down The House: The Inside Story Of Six M.I.T Students Who Took Vegas For Millions, Robert Luketic's new film is a high stakes drama about a group of academically gifted youngsters who risk everything in the gambling capital of the world.

Unlike its risk-taking protagonists, 21 plays safe at every turn, sticking with two-dimensional characters whose emotional journey is far too straightforward, then going bust with an obvious double-bluff that we can see coming well before the hapless fall guy.

The hero of this lacklustre yarn is Ben Campbell (Sturgess), one of the most gifted seniors at Massachusetts Institute of Technology (MIT), who has been accepted to Harvard Medical School and needs US300,000 dollars for the tuition.

A chance to raise the cash presents itself when sexy classmate Jill (Bosworth) recruits him to a hush-hush club run by mathematics professor Micky Rosa (Spacey).

The teacher hopes to teach Ben how to beat the odds at blackjack and outwit old school security chief Cole Williams (Fishburne).

Ben joins Jill, Choi (Yoo), Kianna (Lapira) and cocksure Fisher (Pitts) in the card counting ring, learning a system of subtle signals to ensure they never get caught by Cole or CCTV cameras.

The youngsters head for the Nevada desert determined to impress Micky, but the adrenaline rush of winning big gradually corrupts their souls.

21 lays its cards on the table from the opening frame, and Luketic's sluggish direction does little to alleviate the nagging feeling that we know all of the aces up the film's sleeve well before screenwriters Peter Steinfeld and Allan Loeb deal them.

Bosworth and her young co-stars are wasted in two-dimensional roles, Fishburne glowers in his few scenes and Spacey dusts off another backstabbing scoundrel performance from the repertoire.