Jesse Eisenberg, left, stars as Facebook co-founder Mark Zuckerberg and Joseph Mazzello plays his friend Dustin Moskovitz in David Fincher's film The Social Network. (Merrick Morton/Columbia Tristar)

How do you make a compelling film about the start-up of a website, even one as massively popular as Facebook? The Social Network shows us how it's done.

Director David Fincher and screenwriter Aaron Sorkin have great fun exposing the immature undergrad heart beating beneath Facebook's multi-billion-dollar empire.

You begin with a highly coloured source like Ben Mezrich's controversial 2009 book Accidental Billionaires: The Founding of Facebook, A Tale of Sex, Money, Genius and Betrayal. Then you get Aaron Sorkin (The West Wing) to write the screen adaptation, replete with witty, high-speed dialogue that crackles like autumn leaves.

After that, put his script in the hands of flashy director David Fincher (Fight Club, Se7en), who can give things like writing computer code and arguing intellectual property the suspense and urgency of a thriller. Finally, place at its centre a splendid dysfunctional-genius performance by Jesse Eisenberg and propel the action with a deliciously insistent score by Trent Reznor and Atticus Ross.

The end result is not only engrossing, but also shrewdly funny. Fincher and Sorkin have great fun exposing the immature undergrad heart beating beneath Facebook's multi-billion-dollar empire. Set among the Ivy League elite, it's a kind of Gossip Girl with geeks, and it exploits the irony that the world's biggest online social network was created by people who were socially inept.

Eisenberg stars as Harvard sophomore Mark Zuckerberg, a brilliant, ambitious but spectacularly tactless computer programming wizard who, in the first minutes of the film, is dumped by his understandably exasperated girlfriend (Rooney Mara). In a burst of misogynistic sexual frustration, he creates Facemash, the prototype of what would become Facebook. Hacking into the dormitory records of Harvard's houses, he filches photos of female students and juxtaposes them in pairs on his site, inviting users to decide which one is hotter.

Facemash is a campus sensation that gets Mark into trouble with the authorities but catches the attention of the patrician Winklevoss twins (Armie Hammer and Josh Pence). The duo, along with their dweeb sidekick, Divya Narendra (Max Minghella), have plans to launch an exclusive social network site for Harvard and they woo Mark to help them create it. The Jewish Mark, who is keenly aware of his lower caste status at WASP-infested Harvard, strings them along while independently building his own site with his pal Eduardo Saverin (Andrew Garfield), a Brazilian immigrant and fellow wunderkind/misfit.

Fincher flips back and forth between these heady early days and the subsequent lawsuits served against Mark by the Winklevosses and Saverin. The latter is the more painful of the two, and the film soon becomes a tale of betrayed friendship.

As Mark and his partners begin to expand Facebook's reach beyond Harvard, the business-savvy Eduardo starts canvassing for ads to support the site. But Mark, who finds the idea distasteful, instead falls under the spell of California golden boy Sean Parker (a perfectly cast Justin Timberlake), co-founder of Napster. Sean lures Mark and his team to sunny Palo Alto to join the Silicon Valley community, leaving Eduardo stuck in New York on an internship and out of the loop. It's the stuff of adolescent drama: a cool newcomer drives a wedge between two BFFs – only with world wide web domination hanging in the balance.

Fincher and Sorkin savour the absurdity, taking computer geekdom to mock-heroic levels, complete with its own bold rallying cry: "Refresh!" But under the comedy there lurks a quiet pathos in the figure of Eisenberg's lonely character. In his previous films (The Squid and the Whale, Adventureland), the 26-year-old Eisenberg has established himself as a sort of Jewish intellectual version of Michael Cera. With The Social Network, however, he expunges all traces of likeability to give us a glib, irritating smart aleck with a gargantuan superiority complex.

Jesse Eisenberg, left, in a scene from The Social Network. (Merrick Morton/Columbia Tristar)

His eccentricities – wearing a bathrobe to a business meeting or cargo shorts in the middle of winter – aren't signs of lovable nerdiness, but of a flippant disregard for anything outside his own teeming brain. He's like Howard Hughes in a hoodie (only he can't get girls) or Orson Welles's confident young Charles Foster Kane (minus the charm). Yet he's not impervious to his own inadequacies and Eisenberg expertly conveys Mark's sadness and sense of frustration with himself.

You can see why Zuckerberg is drawn to Garfield's more handsome Eduardo, who has the insouciance of a budding Wall Street hotshot. But that also makes him a more desirable candidate for one of Harvard's snooty clubs, a fact that secretly provokes Mark's jealousy and leads to unresolved tensions between the two.

Timberlake lends his own charisma to the role of Parker, while Hammer and Pence make for amusing stereotypes as the blond, blueblood Winklevoss boys. A pair of over-privileged jocks, they're more than ripe for comeuppance from a vengeful nerd like Mark Zuckerberg. (If you're wondering how Pence and Hammer look identical, it's because Fincher used the same digital manipulation employed in his last film, The Curious Case of Benjamin Button, to replace Pence's face with Hammer's.)

You could complain about the lack of strong female characters. Apart from Mara as Mark's razor-sharp ex-girlfriend and a sympathetic but romantically uninterested lawyer played by Rashida Jones, the young women here are all groupies, bimbos or – in the case of Eduardo's girlfriend, Christy (Brenda Song) – psychos. Then again, this is the world of frats and roomies and bromances, the male-fantasy land of beer commercials and MTV spring-break parties.

People have been skeptical about the idea of a full-on feature film about something as new as Facebook (witness the parody trailers for Twitter and YouTube flicks). But the very audacity of this movie is what makes it both funny and dead-on. There are certain pictures that come to define a particular period in time. I'm guessing that, years from now, we'll look back on The Social Network as the film that captured the speed, chutzpah and sheer unbelievability of the first big internet sensations.

The Social Network opens Oct. 1.

Martin Morrow writes about the arts for CBC News.