Theatre review: 4000 Miles, The Print Room, London

4000 Miles, The Print Room, London (Jane Hobson)

Amy Herzog's play has travelled, well, nearly 4,000 miles: it premièred in New York in 2011 – winning its young author an Obie – while in the UK it opened at the Ustinov Studio in Bath, directed by James Dacre, earlier this year.

The title refers to the epic West to East Coast bike-ride 21-year-old Leo has just completed, which was marred by tragedy on route. But this nicely drawn, often funny drama has narrower horizons, taking place entirely within the Manhattan apartment of Leo's 91-year-old grandma Vera, where he rocks up unannounced at 3am.

Vera's a pretty cool granny though; an avowed old progressive lefty, soon they're bonding over Marx, getting stoned and talking about sex. Sara Kestelman plays Vera with brilliant quicksilver changeability, catching the frailty and the fight: she twitches and worries with her hands, and grasps and gropes her way around the flat (her balance isn't what it used to be). She gets frustrated at losing her words; accusing, when she loses her chequebook. But her spirit's undimmed – she's got a wicked dash of humour and a sharp tongue too.

They're both hippies in their own ways, although when Leo discovers his grandpa's book on Cuba, he acknowledges that while he thinks he's uncynical, it's nothing compared to their generation... Daniel Boyd is good as the slightly lost, wound-licking Leo, a cutely dishevelled, puppyish dude, into biking and escaping to the mountains – an idealism that these days, is it's own sensitive guy-with-a-beard cliché, Herzog suggests.

Emotional scenes with Leo's sort-of girlfriend (Jenny Hulse) lack some spark and chemistry, though it's not really the writing's fault; a later swift hook-up with an art student is cruelly well observed, and very funny. In brightly coloured tights and a headband, speaking in “literally”s and “totally”s, Jing Lusi nails the narcissism and the ridiculous, relentless self-promotion of the Facebook age.

But Herzog has a light touch with all these generational gaps and stereotypes, and a good ear for both dialogue and monologue - that is, the way we tell stories about ourselves. Vera's prattling remembrances and Leo's final explanation of what happened on his journey touch on the absurd, but end up moving. 4000 Miles is actually a small journey - one flat, one family - and doesn't much explore hot-button issues it lightly touches on. But it does offer characters that have true-ringing flaws and foibles, as well as tender hearts.