All you really need to know about 21 is shown in the (excessively) stylish opening prologue before the credits. It's a foretaste of what's to come later in the film—not just the general plot details, the narration, and the visual style, but even some of the "how" that will bring us to that point. You could say 21 reveals its cards too early.
Not that you haven't seen movies like this before. It's become a genre unto itself in the last 20 years, which, for now, I'll refer to as MMM—the Misleading Mentor Movie. Young man looking for big break struggles to make ends meet, becomes persuaded by charismatic Svengali to enter the high stakes world of [fill in the blank], only to confront his core of ethics amidst his runaway success. We've seen it applied to a numerous trades: the stock market (Wall Street), bartending (Cocktail), pool hustling (The Color of Money), investments (Boiler Room), and sports betting (Two for the Money), to name a few. Here, it's set in the world of casino blackjack.
21 is based on Ben Mezrich's best-selling book Bringing Down the House, which in turn was inspired by the true story of Jeff Ma, who, along with a team of fellow M.I.T. students, developed an intricate system for card counting in blackjack. Contrary to popular belief, card counting is not illegal—provided no added technology or outside device is being used—but the strategy is strongly discouraged by casinos since it can lose them lots of money. In the case of Ma and his buddies, they were beating casinos for hundreds of thousands of dollars at a time.
A premise with strong potential, but here it's applied to familiar MMM conventions. Jim Sturgess (Across the Universe) sheds his British accent to play Ben Campbell, a ...