Cara Delevingne plays a cut-out rebel in a Young Adult blockbuster that will please fans and bemuse everyone else

Before his The Fault in Our Stars became a fangirl phenomenon, the novelist John Green wrote a minor Young Adult hit called Paper Towns, which, in the wake of box-office paydirt, has now been fast-tracked to adaptation. We begin with the moment that pubescent neighbours Quentin and Margo first clap eyes on each other as children, and become briefly inseparable, before becoming, well, separable, in the way that teenagers of the opposite sex frequently do.

The film spends a long time twigging what we guess is the case fairly quickly, which is that its lead female character, played by Cara Delevingne, is a practically imaginary dream girl – a fiercely inscrutable cut-out rebel, her main function being to disappear helpfully half an hour in. The teenage Quentin is played by Nat Wolff, who narrates in starry-eyed fashion what Margo means to him, and how he must track her down at all costs.

He has yet to realise that she’s barely a character, more a collection of rock-hard clichés with a screw-the-world attitude. Between the two of them, the puckish Wolff and impressively blasé Delevingne could form an eyebrow master-race. They gaze across the city at night from a deserted office building, and she describes it as a paper town, full of paper people. In a quotation from The Dark Knight, Delevingne hangs out of a car window at speed, letting the wind whip through her hair. The difference is that Heath Ledger’s Joker wanted to watch the world burn, whereas Margo mainly wants to stick Post-it notes all over it, telling friends she hates them now, and spelling out her words with capital letters randomly strewn among them.

Eyebrow master race: Nat Wolff and Cara Delevingne in 'Paper Towns' Credit: Michael Tackett/Twentieth Century Fox via AP

Although Delevingne has much less screen time than the poster would indicate, she does well with the part: her formidable self-assurance feels like a solid first stride towards stardom. In a burst of scorched-earth fury at her unfaithful boyfriend, Margo deserts school and the film, which recomposes itself to become more of an ensemble, mystery-solving, road-trip-to-nowhere adventure – imagine The Goonies with an indie-electronica soundtrack and no villains or interesting locations to speak of. “Paper towns” are actually fictitious settlements on maps, and it’s to one of these Margo may well have gravitated.

She’s littered her bedroom with clues, from the photos of derelict Americana on her wall, to the copy of Walt Whitman’s Leaves of Grass by her bedside. Quentin duly picks up the crumbs, convinced she’s beckoning him to some happy-ever-after. His buddies Ben (Austin Abrams) and “Radar” (Justice Smith), who make things even worse by calling him “Q”, seem less convinced by the whole premise, but happily come along for the ride, as does Lacey (Halston Sage), a estranged friend of Margo’s who wants to set the record straight.

Director Jake Schreier (Robot and Frank) deserves some credit for the spark and timing of his ensemble – the supporting cast, especially Abrams and Smith, come close to winning you over, but they can’t disguise the mechanical, one-sided insights where this story’s centre should be. In Lacey, the film has its chance to offer an alternative, “realer” female character than the one Delevingne gets to play, but it tellingly and completely messes this up. Cursed by her ridiculous good looks, she manages to get out the words “I have a brain”, but never to back the claim up with any real evidence.

In a change from Green’s book, Radar’s girlfriend Angela (Jaz Sinclair) is also permitted to tag along, but even this feels like too little, too late. The script makes Quentin realise he’s mythologised his first love to an alarming degree, but offers no solid counterpoint to these puppy-dog fantasies: what we get is a paltry epiphany, long in the coming. Wolff has something, Delevingne has something, and no doubt the book had something, too – its devotees should find enough here to warm to, while the rest of us look on slightly bemused.