When I was growing up, I used to imagine that I was the star in my own movie. That my adventures on the playground or walks home from school were shadowed by an unseen camera crew, recording my every experience for an enraptured audience. While the idea was ridiculous in its egotism – who would care to watch? – there’s some sense of the authenticity of the everyday, an observation of the simple joy of growing up to be found in Boyhood, Richard Linklater’s latest picture.

You’ve probably heard of the incredible story behind Boyhood by now. Filming for roughly two weeks a year over twelve years, Linklater followed the growth of one boy – Mason, played by Ellar Coltrane – from infanthood to his late teenage years, alongside his mother (Patricia Arquette), often-absent father (Ethan Hawke) and sister (Lorelei Linklater, Richard’s daughter). The camera drifts through Mason’s world, an occasional and unobtrusive presence. Linklater uses the languorous rhythms he perfected in his Before films to create a bond between audience and character that is engaging and laid-back. The careful balance ensures that emotional power can be found in the smallest formal divergence; a zoom here, a long shot there.

The film is essentially undramatic. We observe Mason’s maturation with a subdued sense of wonder, a warm atmosphere occasionally punctuated by conflict, but never penetrated. It doesn’t necessarily feel entirely natural – there’s always the sense that you’re watching a scripted story – but it avoids the self-contained, restrained falseness that defines so many coming-of-age tales. Things are rarely neat, or cyclical; important people and places drift away because that’s how life is.

Ellar Coltrane is the heart of Boyhood; like watching an extended television series or, say, the Harry Potter films, there’s something almost miraculous about watching a boy transform into a man before our eyes. I couldn’t help but wish the film found a different focus, however. Lorelei Linklater’s performance is so engaging: Girlhood might have made for a better film. Arquette and Hawke are both excellent – especially Arquette, who’s never particularly impressed me before. Coltrane is convincing as a wide-eyed youth in early scenes, but – understandably – feels more “actorly” delivering more extensive dialogue as he ages, as though he’s finding his way through a high school play.

Boyhood stands as a recent-history time capsule, chronicling the minutiae of the last decade or so: Gameboy Advance to Xbox to Wii; Phone calls to Facebook to FaceTime; lingerie catalogues to internet porn; and Coldplay to Phoenix to Gotye. The soundtrack demonstrates Linklater as maybe the best modern curator of pop music (possibly exceeding Tarantino) – if you’ve ever wondered “What song will people use to indicate 2005 in the future?” well, wonder no more. Every film is a kind of time capsule of its era, of course, but there’s something nostalgically intoxicating about watching the evolution of pop culture over a decade. Attempts to touch on more significant cultural touchstones – the Iraq war, for example – are more heavy-handed, and consequently less effective.

The undisguised temporality might suggest a film that tries to capture the heft of the ‘noughties’ decade within its sweep. Instead, interestingly, Boyhood’s themes and philosophies are almost anachronistic, inspired by Linklater’s Slacker philosophies. This isn’t especially surprising – I gather this is as much a story of Linklater’s childhood as Mason’s (and is that the director himself cameoing as a ranting lunatic in a late scene? I couldn’t be sure). It’s not hard to hear a middle-aged voice coming through as Mason discusses his choice to delete his Facebook page because everyone’s obsessed with screens.

What, precisely, is the point of Boyhood? I’m not sure it particularly matters. This is a captivatingly entertainingly film, one that breezes through its almost-three hour runtime. The prominent role played by the consistently flawed father figures – variously absent, drunken or abusive – in Mason’s life suggests there is a purpose to the film. At one point, Mason’s father advices him to “Let ‘em know you’re a man who knows what he wants.” Boyhood is about the impossibility of that statement, of trying to “be a man” when there’s no man to look up, and of trying to become who you are without ever truly knowing what you want.