I first met Dean and Sal not long before I left university. At the time I had been buried in books and academia for more than 10 years, diligently working towards a career in the law. However expectations, those of my parents and myself, were beginning to weigh me down. The more I tried to conform to others' thoughts of success and fulfillment, the more I became frustrated with the world and my place in it. I craved liberation. Jack Kerouac's existential tale of dreams, dames, kicks and characters set me free.

"Desirous of everything at once…" Hmm.

"I like too many things and get all confused and hung-up running from one falling star to another till I drop." Sounds familiar.

The philosophy of the writer and his coterie (Ginsberg, Corso etc), later nicknamed the Beat Generation (and packaged and marketed to young America) really awakened something in me. Our times are unquestionably different but their revolt is one that every generation is drawn to; a natural impulse to want to progress and evolve. Before the Beats it was the "Lost Generation" of F Scott Fitzgerald. After them came the peace-loving hippies protesting against Vietnam and Cold War. As Bergerot and Merlin explain in their book The Story of Jazz – Bebop and Beyond, "In the fifties, as McCarthy's campaign against Communism progessed, and the United States plunged into the cold war, cultural life was at a peak. The anti-establishment writers of the Beat Generation often referred to jazz in their work and participated with the California musicians in experiments combining music and literature. Preceding rock and roll, West coast jazz was the expression of youth in rebellion against the middle class from which it came."

Challenging the complacency and prosperity of post-war America hadn't been Kerouac's intent, though. His cause was a personal one. He was a restless, introspective soul who wanted to get closer to the essence of life. For him, that meant new experiences and constant experimentation. His will to live, a howl for spontaneity and possibility, really appealed to me. Former Smash Hits and The Word editor Mark Ellen, who recently wrote a moving piece recalling a trip he made in 1977 in homage to the book with his then-girlfriend, suggests what made millions long for this mishmash life trailing around the Promised Land of the West: "Part of the rhythm of this deathless memoir was its manic urge to expose every nerve-ending to the elements, a mission rendered impossible by the air-conditioned transport of the modern world. Kerouac marinaded his readers in all the scented flavours of his vast and exotic homeland – sights such as the thunderheads over Bear Mountain and 'the sun the colour of pressed grapes', the sound of its juke joints and rattling boxcars, the soft fragrance of wood smoke and chilli beans as he neared the Mexican border. At one memorable moment he watched the Mississippi river 'with its big rank smell that smells like the raw body of America itself'."

On the Road opened the mind's eye and showed people the way, both figuratively and literally. As Ellen points out, "The network of interstate highways was in place in the late forties but used mostly for commercial traffic. No one had explored its real potential. Kerouac's adrenalised bursts from coast to coast in a blizzard of speeding tickets somehow made the country seem smaller. You could drive from New York to LA on six tanks of cheap fuel! The endless big-sky landscapes were a metaphor for the limitless possibilities of mental and physical adventure, and your classless ragtag band of fellow travellers were the portals to a brave new liberated world."

Just as the book tends to divide opinion – some find it reckless, self-indulgent and incoherent, believe it or not – the news of a film adaptation has also provoked mixed reaction. Translating Kerouac's vision of "spontaneous beat prosody" to the big screen is impossible, some say. As foolhardy an attempt to render prose in film as a director tackling Joyce's Ulysses, Orwell's Animal Farm or Fitzgerald's The Great Gatsby (no pressure, Baz Luhrmann). Consider also that the Beats have had a bumpy ride in Hollywood and it's taken executive producer Francis Ford Coppola more than 30 years of struggle to realise his dream since he first acquired the rights. Perhaps some books are best left on the shelf.

So it was with great trepidation that I walked into the Clapham Picturehouse and took my seat to watch Walter Salles' interpretation of the book. Salles, of course, was the man who brought us another wanderer's tale of coming-of-age revelry, The Motorcycle Diaries, starring Gael Garcia Bernal as a young Che Guevara who biked across South America with his friend Mial in 1952. WIth the cinematographer of that film, Eric Gautier, also on board, this film would certainly look authentic and be visceral, whether shooting in a Des Moines juke joint or capturing a hazy Californian desert through the speckled lens of an old beat up Hudson.

The film remains faithful to the book, which documents the adventures of a thinly disguised Kerouac and his yea-saying muse Neal Cassady as they tear across America in the forties. The synopsis: "Just after his father’s death (although in the published Penguin version the catalyst is his failed marriage), Sal Paradise (Sam Riley), an aspiring New York writer, meets Dean Moriarty (Garrett Hedlund), a devastatingly charming ex-con, married to the very liberated and seductive Marylou (Kristen Stewart). Sal and Dean bond instantly. Determined not to get locked in to a constricted life, the two friends cut their ties and take to the road with Marylou. Thirsting for freedom, the three young people head off in search of the world, of other encounters and of themselves."

Along the way Sal hears the call of jazz after witnessing a Bird-like Walter (Terrence Howard) riff into the night, shambles after Dean and Carlo (aka Allen Ginsberg played by Tom Sturridge) as they get close in Denver, shares time with Terri (Alice Braga) while working in the cotton fields in California, checks in with Old Bull Lee (Viggo Mortensen brilliantly channelling the William Burroughs character's "critical anti-everything drawl"), watches Dean ping pong from one girl to the next (via the odd indiscretion for money with Steve Buscemi) leaving dejected current wife Camille (Kirsten Dunst) holding the babies and is later abandoned himself after contracting dysentery following a drug-fuelled jaunt in Mexico. There are countless other adventures, of course.

Salles and his cast spent several weeks at their "beatnik bootcamp" immersing themselves in the texts and the characters. The director was striving for both authenticity and spontaneity. He was also trying to honour the original 120-foot teletype roll of taped together tracing paper, the first draft that is currently on display at the British Library. In this version Salles noticed  that the "search for the father leitmotif was so much more present" that he and scriptwriter Jose Rivera decided to explore that theme together with the more familiar arc from youth to adulthood.

He has made a thoughtful and respectful film no doubt, particularly in picking away at the legend of carefree chameleon Dean Moriarty/Neal Cassady, the mythical figure who had an extraordinary effect upon others – not least Allen Ginsberg, who proclaimed him a "secret hero of these poems, cocksman and Adonis of Denver" in his seminal poem Howl. Cassady would later be the inspiration for the main character in Ken Kesey's One Flew Over the Cuckoo's Nest, as well as countless road songs. By telling the story of the Beats "through the offbeats", Salles reminds us that freedom comes at a price; if we don't make the sacrifice then others will have to on our behalf.

That is not to say that the director has turned On the Road into a cautionary tale, but the notion of journey – a life spent riffing on moments – was Kerouac's main literary motif and should have come through more strongly. It was for that reason that I came away from the cinema feeling rather numb. The film delivered all the shenanigans – sex, drugs, jazz, joyrides – but dampened the spirit. This is because Kerouac's rich and vivid passages had been transposed to a plot that struggles to resonate on quite as many levels. It is no coincidence that the two most striking moments in the film involve a coarse RIley reading key passages as they bring to life the story more than any visual ever could: the hallowed "mad to live" quote and the blissful reverie of "I think of Dean Mor-i-ar-ty", which closes the film. The final moments where Paradise, fueled by coffee, pea soup and benzedrine, pieces together the past five years of his life, breaks his writer's block and plays one big solo on his typewriter is also very effective. 

The challenge is how do you articulate ecstasy and joy? That state of becoming? The giddy heights of human experience, where we make our lives in the unknown. It is challenging enough to do this in words, let alone through the medium of film where the balance between the vivid and the more explicit is so key to telling a story that can simultaneously evoke strong feelings and engage an audience in little over two hours.

Apart from the 'kicks and hits' approach of Salles in the film, casting is questionable – Hedlund is handsome and charismatic but he's not mad  as a "Holy Goof" should be, while Riley is not the football-playing man with beating heart that made Kerouac the romantic such an intriguing figure. Carolyn Cassady, widow of Neal and one-time lover of Jack, recently questioned why they had chosen such "wimps" – a little harsh but I can see her point. She also hit upon another dimension to the relationship between the leads, mirroring that of Kerouac and Cassady, that doesn't come across well enough: “They each had what the other wanted. It made them admire each other more.”

Though you may tingle at some point during On the Road, ultimately Salles and Rivera can't connect us to the emotional essence of Kerouac and the Beats. A recognition that, in the words of affiliate John Clennon Holmes: "They were actually on a quest and that specific object of their quest was spiritual. Though they rushed back and forth across the country on the slightest pretext, gathering kicks along the way, their real journey was inward; and if they seemed to trespass most boundaries, legal and moral, it was only in the hope of finding a belief on the other side."