Currently playing in theaters: "The Social Network"

David Fincher's extraordinary The Social Network opens with a simple scene that serves as a template for everything that is to follow. In a crowded restaurant, two college kids are out on a date. Mark Zuckerberg (Jesse Eisenberg) goes to Harvard, while his girlfriend Erica (Rooney Mara) attends Boston University. Over drinks, Mark prattles on about having gotten a perfect score on his SAT and the difficulties of getting into final clubs (Harvard's oldest and most elite fraternities).

Erica moans about having a lot of homework to plow through, but Mark dismisses her complaint ("You don't have to study because you go to B.U."). "Dating you is like dating a StairMaster," Erica observes about Mark's rat-tat-tat thought process and is left agog at his capacity for casual, thoughtless cruelty. The scene ends with an angry Erica breaking up with Mark, eviscerating him with an observation so cutting it sets in motion events that will lead to the creation of Facebook - and make Mark the youngest billionaire in the world.

The Social Network was written by Aaron Sorkin (The West Wing, Sports Night), who packs two movies' worth of dialogue into two hours at a rollicking, dare-you-to-keep-up speed. Directed in plain, unobtrusive style by Fincher, the film consists mostly of people talking as it cuts back and forth between Harvard in 2003-04 and the legal depositions that take place several years later.

But despite the ceaseless yammering, The Social Network delivers the heady, rib-tickling rush of an action picture, and it gradually builds to an emotional wallop that blindsides you. When it's over, you immediately want to watch it again to figure out how the filmmakers pulled off the trick.

Initially, the movie seems to be a detailed recreation of the motivation that led Zuckerberg - an intensely awkward, fiercely intelligent kid with perhaps a touch of Asperger's and a restless ambition - to create a website for Harvard students to chat and interact. According to the movie, Zuckerberg stole the idea for the site from the twin jocks Tyler and Cameron Winklevoss (both played by Armie Hammer in a wonderfully witty, entertaining manner), who rowed crew for Harvard, and their frat brother Divya Narendra (Max Minghella). The three first approached Zuckerberg for his computer skills and later successfully sued him for $65 million.

To fund his website, which was initially called thefacebook.com, Zuckerberg turned to his only true friend Eduardo Saverin (Andrew Garfield), who became his business partner and tried to monetize the enterprise as the website's popularity grew. But Saverin, too, ended up suing Zuckerberg, settling for an undisclosed amount rumored to be in the hundreds of millions.

The story behind the creation of Facebook is interesting enough, but what makes The Social Network soar - what makes it easily the best movie of the year thus far - is its insights into human behavior. Harvard is depicted as a privileged microcosm with a set of rigid social and class delineations mirroring those of the outside world. When lonely, bitter Zuckerberg holes up in his dorm room, the film cuts to decadent parties across campus (are they real, or are we seeing what he imagines popular kids are like?). His alienation and longing to belong curdle into disdain.

Eisenberg plays Zuckerberg as a genius incapable of suffering fools. He only maintains eye contact with people he looks up to or respects: Eduardo, visiting lecturer Bill Gates (playing himself) or Napster founder Sean Parker (an exceptionally suave Justin Timberlake), who eventually secures the funding necessary for Facebook to expand globally. Zuckerberg is a prickly, secretive outcast - a nerd smarter than everyone else in the room - and through his story, The Social Network captures the way society casts people in roles that are often difficult, if not impossible, to escape without radical action. There is no small irony in the fact that Zuckerberg decided to build a network for interacting with the world the way in which he was most comfortable - via a computer keyboard - and 500 million people followed him.

The Social Network doesn't take sides on the ethics or morality of what Zuckerberg did, although Saverin, played with great empathy and likability by Garfield, could be considered the film's true hero - a man who stood by his friend when no one else did and trusted him, only to be stabbed in the back when his services were no longer needed. Because of the subject matter, The Social Network has the feel of a zeitgeist movie: "You write your snide bullshit from a dark room because that's what the angry do," Zuckerberg's ex-girlfriend snarls at him, essentially defining - and decimating - much of the contemporary blogosphere. In cyberspace, the lonely and unloved have an outlet for their rage and pain. Zuckerberg just happened to figure out a way to get rich voicing his.

The Social Network is a snapshot of our brave new world and its permutations of eternal human emotions, and, in Zuckerberg, it finds a perfect poster child for its message. "I'm not a bad guy,'' he says at one point in his own defense. By the end of this rich, dense, dazzling movie, you agree with him