Youth in Revolt / The first unwritten rule in judging a film is to not judge it by the book on which it’s based. But when the book in question is Youth in Revolt, the beloved 500-page tale of teen angst and alienation, it’s hard not to revert back to the source material. And there’s a lot of material, hence why the bestseller, based on the debut book by San Francisco Bay Area writer C.D. Payne (who has penned three sequels) has been in production limbo for almost two decades. MTV and Fox television filmed a pilot for a television series that never got off the ground, and the story was converted to an unsuccessful stage play, while rumors of a film project lingered for many years.

The difficulty in adapting the novel, one presumes, is the journal style in which it’s written. Reminiscent of blogs before anyone had conceived of such an idea, the book has a day-to-day unfolding that brings forth a cast of characters that total more than 25. The story follows the misadventures of Nick Twisp, a 13-year-old who is too smart for his surroundings. Nick is constantly writing, both in long hand and on his computer, about his trials and tribulations, mostly involving the opposite sex, as his surroundings as well as his friends and neighbors constantly change.

That’s the biggest problem with the film version, released last Friday after numerous delays (the film was originally slated to release in October). In trying to connect plot points while simultaneously excising the majority of the novel’s characters, it becomes a CliffsNotes version, giving us the payoff with no buildup, and reducing star players like Ray Liotta, Fred Willard and Steve Buscemi to walk-on cameos (even listed in the opening credits as “Special Appearances”).

But the film (and the novel) is primarily about Nick, from Nick’s point of view, and the eternally nebbish Michael Cera takes on this role with relish, even if it is primarily a character he’s played since Arrested Development. He’s nervous, he stutters, he can’t keep a clear head when a woman walks into a room–he does all the things that Michael Cera has done a half-dozen times before. His parents are aging, selfish, sex-starved reprobates, trying to starve off loneliness with his dad (Buscemi) hooking up with younger strumpets in exchange for a place to live, while his mother (Jean Smart) wears dresses with necklines plunging far below her self esteem. Nick watches all of this in horror, fuming that everyone is having sex except for himself.

So when he finally meets the girl of his prepubescent dreams (newcomer Portia Doubleday) who faults him for acting like…well, like Michael Cera, he adopts a new persona, that of superbad Frenchman Francois Dillinger. Francois has a pencil-thin mustache, smokes, mouths off to authority and has no compunction to more felonious crimes, all to impress his love. Finally able to shed his own typecasting, even if he has to play most of the scenes together in duel-persona camera trickery, Francois is a guilty pleasure, a man who keeps pushing further than reason or safety allows, and it’s watching the battle of both of Cera’s characters trying to save each other from himself, that saves Youth in Revolt from being an unwieldy, underwritten yet ambitious mess–but just barely. Without the dueling Ceras, Youth in Revolt could very easily have sunk into the poor sex romps of the past few years (think Sex Drive and College), with its almost sitcom-styled wackery and familiar setups, including the age-old staple of (insert groan here) sneaking into a girl’s dormitory.

Still, with all the teen-sex-starved comedy firmly in place, director Miguel Arteta (The Good Girl, Chuck & Buck) smartly manages to occasionally break convention long enough for some real laughs before sinking back into the relatively safe sex storyline. At its worst, Youth in Revolt comes off with passable marks of a genre with notoriously low points. At its best, it might inspire those who haven’t read Payne’s novel to undergo its 500 riotous pages. And that should be considered a worthy goal.