Because the original Watchmen graphic novel is not your standard comic book. (And yes, nit-pickers, it is a graphic novel -- though it was first published as 12 individual issues, it was always intended to tell a single story from beginning to end. It may be printed in the "trade paperback" format now, but there is no Watchmen Vol. 2. So there.) And while many reviewers might disagree with me, the film version of Watchmen is not your standard superhero movie. True, it has guys in costumes fighting street-level thugs -- and, later, other costume types -- with the same martial-arts moves you'd see in any of the Batman flicks. But the big difference is that this isn't an origin tale, like Batman Begins or Iron Man or most other superhero films. It's the opposite of an origin, where the heroes are out of the spotlight on the other side, slowly dying and being forgotten about as they reflect on their lives. True, some of the heroes remember their origins over the course of the film -- the masked detective Rorschach explains how he was scarred as a child (and further scarred as an adult), and walking A-bomb Dr. Manhattan remembers being torn apart and pulling himself back together -- but everyone else simply exists as a familiar archetype, forcing the audience to use their brains and piece together their stories from jokes and implications, like a game of Memory. It makes you use your brain even as it punches you in the stomach, in the best way possible.

Keep in mind that the book doesn't give all of their origins, either. In that way, the movie is remarkably faithful to the book, and everything Snyder cut out was pretty much expendable, if any element of one of Time magazine's 100 greatest novels of the past 80 years can be said to be "expendable." Side stories with minor characters who tangentially interact with the main ones are left as cameos: the newspaper vendor, the New Frontiersman staff, Rorschach's psychiatrist, Captain Metropolis, etc. Certain redundant flashbacks have also been excised. (Ozymandias's origin is one of the few that's in the book and was cut -- it would have been nice to see that one on-screen, but it's not really necessary.) And although the action of the movie has certainly been ramped up, these are still reflective heroes, which means that when they're not punching people, they're engaging in a not-insignificant amount of dialogue, much of it in voiceover. Reviewers can trash-talk the action, but if not for the occasional exploding person or snapped neck, all the talking in this film would have driven me insane, especially when it's Dr. Manhattan doing the gabbing, one of the film's few weak spots. It's not that he talks too much, it's just that Billy Crudup can put me to sleep on a normal day, and when he's trying to sound all HAL 9000, he's like a blue Valium. Rorschach's gravelly voiceover -- which is a little too close to Christian Bale's Batman for my tastes -- at least has some good one-liners.

But given what Snyder was tasked with doing, the man did a bang-up job, creating a better adaptation of a book than any of the Harry Potter movies, one that isn't afraid to be as dense as its source material. Is the Watchmen movie more streamlined? Yes. Is it still massively complicated? Absolutely. There are two teams of heroes to keep track of from two different eras -- plus one hero, the Comedian, who travels in both. And the movie, like the book, is approximately 50% flashback, which makes things even more difficult to follow as we bounce from an alternate 1985 to an alternate 1945 to an alternate 1965, trying to figure out who would have killed the Comedian when all of his enemies are dead, mostly at his own hand. It's a lot to take in, especially for someone who hasn't read the book. Hell, even the premise of the movie is hard to explain to a layman. If it'll help, here are three simple ways to describe it, using existing films:

300 meets Mystery Men
A team of ragtag, fairly ridiculous superhero stereotypes in skimpy outfits have to go up against a deranged villain with far-reaching fingers -- in slow-mo -- when the most powerful hero in town vanishes.

X-Men: The Last Stand meets The Godfather II
A team of superheroes see one teammate die and another become an all-powerful killer as flashbacks tell us how the actions of their predecessors got them where they are now.

Batman Returns meets Eternal Sunshine of the Spotless Mind
Vinyl dollies and rubber-suited boys do battle and hook up with each other while trying to make sense of past events that wreak havoc with the narrative structure.

Still interested? Good. If you're willing to invest all of your attention and 2 hours and 43 minutes of your time, it's totally worth it. Don't wait for the DVD -- the screen will be smaller, and the movie will keep getting longer. And remember that there will be no sequel, so this is your only shot. There are a couple of conditions, though: you need to be able to accept the everyday reality of a costumed superhero, and you need to wrap your head around multiple character threads that intersect at various points in history, told out of sequence. If you can do that, then this movie may be as rewarding to you as the original comic book is to comic geeks. (And if you like the movie, both Snyder and I highly recommend that you read the comic book next.)

If you're a comic geek like me, you have even more conditions. You need to be able to accept that the movie is not the book, and no movie ever could be. You need to be willing to acknowledge that some of the changes that Snyder made actually improve (yes, I said it!) on the original story, at least in terms of what works on film. And you need to accept that pretty much ANY R-rated movie with a budget this size is going to need to play up the sex and violence in order to justify its price tag and rating. If you can do that, then you, too, will enjoy the hell out of it. ...Of course, if you hate Zack Snyder's 300 -- and while I don't agree, I can certainly understand why you might -- then you may get angry when the characters fight in slow-motion, and that happens a lot. But there was a lot less going on in 300, both content-wise and pallette-wise, than there is here. Almost as many naked men, though.

Watchmen opens March 5 at midnight, in IMAX theaters and those whaddayacallem theaters that aren't IMAX. The film is rated R for exploding bodies, compound fractures, frantic humping, hog shots and smoking.

Need more info? Read our complete guide to the world of Watchmen! Already seen it? Check out my colleague Dan Manu's spoiler-filled analysis of the movie's successes and failures. Then tell us what YOU thought of the movie in the comments area below or in our Watchmen forum!