Edna O'Brien's first novel, banned by Ireland's censors in 1960, burned by her own parish priest, is more than a coming of age tale. It is a story of sexual awakening. Two teenage girls, Caithleen Brady and Bridget Brennan, known as Kate and Baba respectively, take flight from their sleepy rural lives for the wilds of Dublin. Doing so means swapping the sexless prison of a Catholic convent school for the prospect of a lustier, livelier existence.

Green, grassy moss covers one half of Richard Kent's stage; grey brick and stone the other. This is a piece about divides – between town and country, yes, but also men and women, childhood and adulthood, and between the two young girls themselves. Kate is a bookish soul, a scholarship girl who sneaks James Joyce past the nuns, while the vivacious Baba leans on her looks and leads her best friend astray. She slaps her father's cow's udder unction on her best friend's flat chest ("We must, we must, develop our bust"), before getting them both expelled by speculating on the sisters' sexual habits.

No matter – in 1950s Ireland, all a country girl needs is a fella to look after her, and Dublin has plenty. Genevieve Hulme-Beaman plays Baba with a studied sexuality, smiling over her shoulder like a vintage pin-up, while Grace Molony's Kate struggles to find her feet in high heels, always rolling her ankles with a girlish discomfort.

Their friendship is far more fully felt than either of their first flushes of romantic attraction. If the men in Lisa Blair's staging seem like shadowy figures, silhouettes smoking in the dark, both sexy and threatening, they flatten out when they step into the main story. Kate's older, married admirer, Mr Gentleman (Valery Schatz), is little more than a grey suit and a French accent, while the two caddish spivs that pick the girls up off Dublin's streets are altogether unseemly: sharks in smoking jackets with wandering hands and hoarse laughs.

O'Brien's own adaptation suffers from what we might call the synoptic problem – a regular affliction incurred in page-to-stage transit. Her novel is much more than its bare-bones plot. In seeing the world through Kate's naïve eyes, it lives in misinterpretations, feelings and observations. Onstage, it becomes a trot through events, and a rushed one at that. There's little sense of excitement or emotion, though Blair's production fares better with Kate's bewilderment.

If it's more about ideas and images than feelings (compare Sally Cookson's Jane Eyre) that feels rather dated, and The Country Girls sometimes sinks into set-text territory. Its themes float to the surface: Ireland's lyricism and alcoholism go hand-in-hand, as do repression and religion, and the sense that the city's crowds can be just as lonely as countryside convents – especially for young women coming of age.

The Country Girls runs at the Minerva Theatre, Chichester until 8 July.