The Aliens, Bush Theatre, London

The veteran director Peter Gill makes his belated debut at the Bush with this sensitive, beautifully acted production of The Aliens, our first glimpse in Britain of work by Annie Baker, the much-lauded young US dramatist. It's a deceptively slight piece that, while it can't live up to the plaudits of the New York critics (who reached for comparisons with Chekhov and Chardin), evinces a real talent for the kind of gentle humour that illustrates how the sadness and the silliness of life are interwoven.

The setting is the dreary back patio of a coffee shop in Vermont – the illicit haunt of two slackers in their early thirties. Ralf Little brings a lovely, dreamy-eyed quality to KJ, the college dropout (who lives with his New-Age mother and drinks tea spiked with psychedelic mushrooms), while also dropping haunting hints of the mental vulnerability that will come to the fore later. The bony Mackenzie Crook is all wiry edginess as his pal Jasper, a Charles Bukowski-freak who is channelling his bitterness at a failed love-affair into the composition of a sub-Kerouac novel.

This pair of losers, who once played in an abortive band called The Aliens, seem like the height of cool to Evan, the nervous high-school student who has a summer job at the shop. His painful awkwardness, apprehensive curiosity and aching need for adult acceptance are brought to brilliantly funny and poignant life by the curly-mopped, boyish Olly Alexander.

Baker could have mocked the doomed pretensions of the older men through this character's jittery, misguidedly over-awed reaction to them. In fact, Evan's presence exposes the odd integrity that's in tension with their absurdity. The song they perform from their back catalogue is full of goofy charm and, as the flashy public fireworks explode in the sky, there's an affecting loneliness as well as loopiness in their alternative Fourth of July celebrations.

To 16 October (020 8743 5050)