Directed by: Robert Luketic

Starring: Jim Sturgess, Kevin Spacey, Laurence Fishburne, Kate Bosworth

MPAA rating: PG-13 (slight violence, slight sexuality)

Running time: 123 minutes

Best suited for: gamblers, caper lovers, beat-the-system fans

Least suited for: Anybody who thinks the book is unbeatable

The buzz is this: "Well, it's not as good as the book."

Okay, so name one movie that is. Wait a sec- maybe "The Godfather." Maybe Elmore Leonard's "Out of Sight" (George Clooney, Jennifer Lopez), for the last five minutes alone. And maybe everything from Tom Clancy ("The Hunt for Red October," "Clear and Present Danger"), whose books often read like technical manuals. And probably everything from Michael Crichton ("The Andromeda Strain," Jurassic Park"), whose books often read like movie synopses anyway.

The point is, judging a film by the book it's based on is a little like planting an orange tree in an apple orchard and then expecting an orange to taste like an apple.

In 1993, Ben Mezrich wrote a book called "Bringing Down the House," the true story of six MIT students who went to Vegas, counted cards and won several million dollars over the next five years.

The book examines the scenario, explains the minutia of beating the system and explores the inner angst of realizing casino thugs will kick in your teeth if you're caught.

If you're into Vegas, yes, the book's a good read the same way standing eight hours at a craps table and walking away with $200 might be considered a good night.

For gamblers (more than 1 million of whom read the book) it was a rush they could understand.

Moviegoers typically enjoy a different sort of adrenalin rush, living vicariously by scripted events unfolding before them in a precise, stylized manner. And in that regard, "21" delivers- well- in spades.

The film is based loosely on the book- so loosely that Jim Sturgess, who plays MIT student Ben Campbell, is Caucasian; in reality, Jeff Ma, using the alias Kevin Lewis in the book (in case casino thugs eventually did find him and kick in his teeth), is Asian.

In the film, expect a kind of slow boil escalation of tension.

A broke MIT pre-med student who's barely even dated is dazzled with the Vegas lifestyle but eventually realizes he's the victim of a double-cross and a con. What, not in the book?

That's what those in Hollywood, those in the biz, like to call "artistic interpretation."

No, the movie is actually very little like the book, but it is very much like a good film, one about gambling and gamblers, and filled with mostly all the right ingredients.

Yes, I do admit to an occasional weekend-in-Vegas habit, to getting that Friday night rush when the neon halo of Vegas peeks over that last desert rise, so I'll also admit that watching people (even actors) raking in all those purple clay chips can get my heart pumping.

I suspect that people who enjoy hanging around Luxor or Circus Circus, or gambling anywhere in between, will like the film more than those who prefer other leisure activities.

But in a sense, "21" becomes a nifty caper film, too, more than simply a film about a bunch of crafty Boston kids who outsmarted the casinos.

The payoff is deliciously rewarding in ways that make me glad I hadn't read the book.

There's a nice change in the way shy, reserved Ben gradually loses himself in the Vegas mystique.

Frequently altering identities, living the life of a high roller, he eventually forgets his original plan- to simply make enough money to get through Harvard Med.

Ben becomes a player, with all the privileges and rewards- and eventual risks- that accompany the life.

Kevin Spacey plays Micky Rosa, the MIT professor with both a capitalistic streak and a slightly sadistic one, who cultivates bright students like a modern-day Fagen.

Spacey has had quite a diverse and illustrious career, although I haven't enjoyed him this much since "The Shipping News"- ah, another film I believe to be better than the book (which won a Pulitzer by the way, while the film did poorly, so consider the source).

Still, I'd say that "21" may do for blackjack players what "Rounders" did for Hold'em players: illuminate those folks in a way nongamblers can understand; paint them in both cunning and vulnerable hues, some likable, some not, and a few addicted to the tables in ways even they themselves can't fully understand.

And just so you know, I saw the film and then read the book.

So which did I like better?

Sometimes it's okay to like apples and oranges, as long as you're aware that each is what the other is not.