Jack Kerouac’s 1957 novel, “On the Road,’’ is regularly classified as “unfilmable,’’ and with good reason. How do you shoehorn a legendary stream-of-consciousness blurt — a work famously written on a 120-foot scroll, as though putting a fresh sheet of paper in the typewriter would just get in the way — into the confines of semi-conventional cinema? Maybe the best approach would be to forget about the Beats, set “On the Road’’ in the modern day, and shoot it on cellphones. Anything to reflect the Day-Glo immediacy of Kerouac’s prose.
Instead, we have Walter Salles’s “On the Road,’’ a straightforward and rather sane version of the events described in the book and, against all odds, a surprisingly effective movie. Salles is Brazilian — he made the 2004 Young Che Guevara movie “The Motorcycle Diaries’’ — and maybe that helps, since he’s reverential toward the Beats without treating Kerouac and company as rebel saints, the way we can. Stolid as this “On the Road’’ often is, it has an outsider’s eye for the beauties of America’s physical and emotional landscape, and it shares the reckless excitement of its young seekers while standing just far enough outside to see the damage they leave in their wake.
And the casting is very strong, especially Garrett Hedlund in the critical role of Dean Moriarty, a.k.a. Neal Cassady, the one character who lives what the others just write about. That’s not quite right: Dean can only live — skipping from city to city, apartment to apartment, woman to woman — while his friends have to turn it into art. That’s why they idolize him: Dean’s life is his art. Kerouac knew there’d be a price to pay for that, and if his book sees the downside of Being Dean with piercing romanticism, the movie just sees it clearly.
Anyway, Hedlund — last seen in “Tron: Legacy,’’ poor thing — is a tremendous Dean, confident, impulsive, sexy, rootless. Even his mistakes seem like great ideas at the time. (It helps if you’re a guy.) The others, also well cast, are lesser planets to his Sun: the Kerouac figure Sal Paradise, played by Sam Riley with a wolfish smile and wide eyes that see everything; Tom Sturridge as Carlo Marx/Allen Ginsberg, burning up with the holy “Howl’’ still inside him; Viggo Mortensen floating briefly in as Old Bull Lee, as gravel-voiced and frightening as his inspiration, William S. Burroughs.
The movie follows the chronology of the book, omitting a lot but hitting the main points: Sal’s romance with the migrant worker Terry (Alice Braga), that creepy Louisiana visit with the oracular junkie Lee and his half-crazed wife (Amy Adams); the road trip to Mexico; the ceaseless triangulation between New York, San Francisco, and Denver. Salles gets the highs of the parties and jazz clubs — Terrence Howard turns up as a Charlie Parker-esque saxophonist — the eroticism and weirdness of sex scenes that can go any which way (and more explicitly than Kerouac managed). He also gets the lows of the mornings after and the bleak dawns on empty highways. And he understands that being true to oneself usually entails being false to someone else.
That’s where the women come in — or, more properly, don’t. If Kerouac acknowledged the problems inherent in being married to a Beat (total unreliability foremost among them), the movie dramatizes them with quiet force. As Dean’s second (I think) wife, Camille — a.k.a. Carolyn Cassady — Kirsten Dunst rides a roller coaster of hope and disappointment, pregnant and housebound with Dean’s infant daughter while he heads out to score weed and chicks. Elisabeth Moss (“Mad Men’’) breathes fire in her brief scene as Galatea Dunkel.
As Dean’s first (and third) wife, the teenage Marylou (Kerouac based her on LuAnne Henderson), Kristen Stewart is getting the lion’s share of the publicity for “On the Road,’’ and she gets a fair amount of screen time, too. It turns out to be one of the “Twilight’’ star’s better performances, well within her narrow range and touching in the way Marylou uses sex as rebellion, only gradually becoming aware of what it will and won’t give her. Usually a tense and sullen actress, Stewart unwinds here; she lets us see the character’s fearlessness, her naivete, and where the two connect.
What this “On the Road’’ isn’t, though, is truly crazy — wild with the thrill of casting off all restraint — and Kerouac himself would probably hate it for that. But Salles has made a movie with more wisdom in it than you might expect, and he hasn’t attempted the impossible task of trying to film the book. He just films what the book’s about, and it serves him well.