There's no doubt that Jack Kerouac's autobiographical 1957 novel On The Road defined a generation - the 'Beat generation' as he termed it, a literary movement driven by sex, drugs, poetry and jazz (rock'n'roll being in its infancy).
Less controversial and a sight easier to follow than Allen Ginsberg's Howl and William Burroughs' Naked Lunch, On The Road remains the Beats' most accessible insight into the unsettled mindset of America's post-war youth.
But for the record, this reviewer gave up on the book as a bloated, cooler-than-thou yawn that belongs firmly in its time. Recreating the mood almost to a fault, Walter Salles' film elicits a similar feeling.
It's 1947 and brooding writer Sal (Riley, Control) is stuck in an existential rut. But his eyes and mind are opened when his poet buddy Carlo (Riley's fellow Brit, Tom Sturridge) introduces him to Dean Moriarty (Hedlund), an irresistible force of nature on a relentless search for kicks – be they sexual, musical or narcotic.
Inspired by his new best friend, Sal grabs his backpack and hits the road to discover what's out there, and maybe find himself while doing it.
Thus begins a three-year odyssey during which Sal drifts back and forth between the coasts for the ultimate American experience, initially alone but mostly with Dean (the alter-ego of Kerouac's friend Neal Cassady) and his equally uninhibited teenage wife MaryLou (a flesh-flashing Stewart).
As long as they have gas in the tank, smoke in their lungs, and plenty of like-minded pals to powwow with, the cosy threesome are happy.
Or are they? The trouble is you never get the sense that Sal is having much fun. Is he doing this because he genuinely wants to or because it's his literary duty?
There's nothing wrong with Riley's performance; his broodiness and twenty-a-day drawl are spot on. It's just that the narrator should never be a film's greatest enigma.
Despite attracting such talents as Kirsten Dunst, Amy Adams, Alice 'I Am Legend' Braga and Mad Men's Elisabeth Moss, On The Road's female characters are little more than killjoys and conveniences. That goes doubly for poor MaryLou, though Stewart wears her object status well.
One scene has the men expounding theories on literature over cigarettes in the study while the ladies are left to discuss the art of fellatio while scrubbing the kitchen floor. Intentionally ironic or not, it highlights the misogynistic streak that runs through Kerouac's work.
Consequently, the male cameos make a greater impression, Mortensen delivering gruff wisdom as legendary writing guru Old Bull Lee (Burroughs by another name), and Steve Buscemi popping up as a fellow traveller who is less by-the-book than he looks.
But only Hedlund's selfish, reckless Dean goes through a significant learning curve as he gradually discovers the downside of hedonism. Consequences and responsibilities, what a drag.
As director of The Motorcycle Diaries, Salles has proven form in the period travelogue stakes. But while the vistas and general Americana are impressively realised, the repetitiveness of the story makes each episode begin to resemble the last.
The narrative might not go far, but you'll certainly feel like you've been on the road. On and on and on.