“On the Road” is now playing at Sundance Cinemas: R, 2:05, three stars out of four.

Who would dare try to make a movie out of “On the Road”? How could you not, in the eyes of the many faithful followers of Jack Kerouac’s counterculture epic, not screw it up? This is an autobiographical book about which not only the events it’s based on have been mythologized, but the writing of the book itself is the stuff of legend. Kerouac famously blurted out “On the Road” in a three-week literary bender, taping the pages into one long scroll so he could write in one uninterrupted explosion.

Yet if anybody dare attempt it, it would be director Walter Salles and screenwriter Jose Rivera, whose 2004 film “The Motorcycle Diaries,” featuring a young Che Guevara, traveled the same highways as Kerouac’s mix of free-wheeling travelogue and consciousness awakening. They haven’t made a film version of “On the Road,” because that would be impossible, but they’ve made a film for “On the Road” fans.

British actor Sam Riley plays Kerouac’s fictional avatar, Sal Paradise, who in the free-wheeling haze of post-war America drifts into the orbit of Dean Moriarty (Garrett Hedlund), who, in Kerouac’s memorable phrase, spend “a third of his life in the pool hall, a third of his life in jail, and a third of his life in the public library.” A two-fisted philosopher-drunk, Dean drapes an arm around Sal and takes him on a nonstop adventure — jazz clubs, poppers, wild parties and above all else, the open road. With Dean’s child bride Marylou (Kristen Stewart) in tow, the film cruises back and forth across the country, its essential fuel Kerouac’s words, delivered by Riley in a convincing imitation. It’s all episodic, with characters drifting in and out of the film without explanation, including Tom Sturridge in what looks like a Ginsberg knockoff, and Viggo Mortensen as a stone-cold William S. Burroughs imitation.

Hedlund is good as Dean, although I think the part works better if you think of him as Kerouac’s reminiscence of Dean (or Neal Cassady, actually) rather than a fully-dimensional person. Dean in the archetype Sam aspires to be, living fully in the moment. But that comes at a cost to everyone around him, including the women — Marylou, Camille (Kirsten Dunst), the mother of his child, and assorted women along the way. The film doesn’t judge, which I think I mistook for acquiescence until “On the Road” kept going, and Dean gradually, and finally, finds himself isolated from the world. The last meeting between Dean and Sal, now married and prosperous, is a heartbreaker. Dean got what he wanted from Sal, Sal got what he wanted from Dean, and the two men go on their way.

Surprisingly, but perhaps wisely, Salles doesn’t try to recreate the heady stream-of-conscious rush of reading “On the Road.” Instead, it’s staged as a rather traditional road picture, with title cards telling us what state we’re driving through, or what the month and year are. Which seems a little odd for a book that was originally written not only without chapter headings, but without even paragraph indentations. There’s something just a little too tidy about it (even the film’s fever dream, brought on by Sam’s bout with dysentery, is an awfully tidy fever dream), especially because there’s no real story to follow here, only encounters and images. But it gives the viewer time and space to really savor those moments, brought to life with Eric Gautier’s gorgeous camerawork, taking us out in the middle of the desert or deep inside the tangled bodies of a Manhattan house party.

The beauty of the images gives “On the Road” a touch of nostalgia, for a long-lost Beat Generation that felt it could change the world, or at least abstain from it. The movie version of “On the Road” won’t have the impact on a person that the book ever did. But it does go some way to explaining why the book did.