THE SOCIAL NETWORK Not pictured: Benjamin Button. Yay!

ONCE UPON A TIME, Facebook was cool. This is an important, if increasingly difficult, thing to remember: Before you got your grandma's friend request, before you moved to Twitter, and before Facebook CEO and founder Mark Zuckerberg made a hobby of merrily blowing off users' privacy concerns, Facebook was cool, exciting, a thing you wanted to be on, the way you found out about parties, breakups, shows, and what your high-school exes now look like.

Times have changed, but that does little to diminish the power of The Social Network, David Fincher and Aaron Sorkin's film about the site's tortured origins. Fincher, back in control after the sap of Benjamin Button, directs as commandingly and deftly as ever; Sorkin's script punches along at lightspeed, telling an endlessly complex story with machined precision.

From its opening scene, it's hard not to be floored: In 2003, in a bar outside Harvard, a geeky undergrad named Mark Zuckerberg (Jesse Eisenberg) has an increasingly intense conversation with his increasingly fed-up girlfriend, Erica (Rooney Mara). Sorkin's razor-sharp dialogue zips back and forth; Eisenberg and Mara's faces begin to subtly strain; tensions rise and rise and snap. And then Zuckerberg, calmly furious, runs—literally, runs—back to his dorm, spiraling into a festering frenzy of drunken blogging and effortless hacking.

And so The Social Network's damningly sympathetic portraiture begins. We never learn where Zuckerberg grew up, who his parents are, or what he wants to be. We only see him as he builds the thing that will become Facebook, possibly stealing the idea from two blue-blood brothers, Cameron and Tyler Winklevoss (Armie Hammer and Josh Pence); clashing with his best friend and initial investor, Eduardo Saverin (Andrew Garfield); getting sketchy advice from Sean Parker (Justin Timberlake), the co-founder of Napster and the closest thing Zuckerberg has to a mentor. Based on Ben Mezrich's book The Accidental Billionaires (which, it should be noted, has been accused of painting these real-life proceedings with a theatrical gloss), The Social Network plays like a finely tuned thriller, growing ever more nerve-racking as Fincher cuts between Zuckerberg's creation of the site and the vicious litigation that followed.

Throughout, Eisenberg grows from a lonely, jilted nerd to the type of guy who has "I'm CEO, bitch" printed on his business cards. This unspeakably clever kid knows he's 10 times smarter than everyone else, and has no trouble letting other people know it—but he's still just a kid. It's an odd role, simultaneously sympathetic and villainous, and Eisenberg's ruthless, oddly charming performance is hilarious, sad, and utterly captivating. (Apparently not getting the memo that one performance this good is usually enough for any film, Garfield and Timberlake turn in some amazing performances, too.)

The characters—and their sometimes idealistic, sometimes earnest, frequently brutal interactions—take the fore, but on closer examination, just about everything else is equally impressive: Fincher's slick, exacting confidence. Trent Reznor and Atticus Ross' hypnotic score. Sorkin's jarring emotional clarity. At one point, Parker tells Zuckerberg what he's created. "This is a once-in-a-generation, holy-shit idea," Parker says, and he's right: Facebook changed the way we thought of ourselves, our friends, our social lives. The Social Network changes how we think of Facebook.