We all live with boundaries, but few of us feel that as keenly as Jenny Erpenbeck, who grew up in the Pankow district of East Berlin, a stone’s throw from the Wall. Now a leading novelist of a unified Germany, she explained several years ago that when the Wall came down in 1989 and the East German state collapsed (she was 22 at the time), a ‘border’ was created between two halves of her life. ‘Without this experience of transition, from one world to a very other one, I would probably never have started writing.’

Set in her old neighbourhood in the dying days of the GDR, her novel Kairos tells the story of the love affair between Katharina, a 19-year-old woman, and Hans, a writer who’s 34 years older, married, with a teenage son. So immediate and intense is their passion – as close as it gets to love at first sight – that they disregard the boundaries they’ve crossed and the inevitability of an unhappy ending.

Before it goes septic, the affair is sexy and ecstatic, a commingling cleverly mimicked in the structure of the paragraphs, with the viewpoint alternating sentence by sentence. It will never be like this again, thinks Hans. It will always be this way, thinks Katharina. Erpenbeck joins the two strands: ‘Then sleep puts an end to all thinking.’

There are early hints that Hans will turn controlling and abusive, despite his best intentions. He thinks ‘it’s important that he sets some conditions, before it’s too late’. He reminds himself that ‘one day he will have to hand her on’. He’s her guide to high culture. The soundtrack the first time they make love is Mozart’s ‘Requiem’; weeks later he takes her on a tour of the Pergamon Altar and points out the battle between Aether and a lion-headed giant: ‘See how close they are… the intimacy of battle? See how alike are love and hate?’ When Katharina is unfaithful (Hans is married, remember), the affair enters a long, dark, unhappy phase. He’s brutally manipulative, she’s unable to break away, and a painful drama is played out in ‘a small country with no easy exit’.

Katharina asks: ‘Will she and Hans be together in a year? Will her country even still exist?’ It’s easy to read Kairos as an allegory, the doomed love affair analogous to the fate of East Germany and the ruin of its socialist experiment, its idealism corrupted by the rigid control of its citizens. But the two questions, uttered in one breath, merit separate answers. A strict allegorical reading can’t do justice to Erpenbeck’s subtle, richly layered, densely allusive and hugely ambitious novel.

Palpably real, the lovers are complex and contradictory. Their miseries register on a human scale, as do their joys. Here Katharina escapes into the arms of another woman:

All night, to breathe and to feel the other’s breath against her skin, or whose breath and whose skin is it? Running her tongue along the other’s teeth as against a friendly fence, feel out with her hands, her lips, her tongue what is dark and moist, listen all night to the sounds of the other, or are they her own? To know the other as herself. One being of flesh and blood joined to another, as by a key. To be one.

Kairos is an impressive achievement that has deepened my admiration for Erpenbeck’s talent for weaving into her fiction clashes of ideology and convulsions of history. But I have to admit that I respected it more than I liked it. As the punishment meted out by Hans to poor Katharina drags grimly on, I grew impatient for the Wall to fall.