Jenny Erpenbeck’s Kairos is one of the bleakest and most beautiful novels I have ever read. On one level, it is a love story, or rather a story about the loss of love. It begins with a woman, Katharina, hearing about the death of her former lover. Boxes of his papers are delivered to her apartment, and when she finally sits down to open them the past rises before her like a pack of playing cards thrown into the air.

The book then moves back to their first meeting, tracing step by step the contours of a relationship that is not only intellectually and emotionally complicated in itself, but whose difficulties are compounded through its relationship to the collapse of East Germany. Katharina and Hans meet in East Berlin in 1986, and they live out the disintegration of all their hopes and dreams, personally and politically, throughout the course of the novel.

Although Kairos is focused on a romantic relationship, it is not really romantic; disillusion seems baked in from the start. When the couple meet, Katharina is 19 years old, with her life ahead of her. Hans is married with a son, an apparently successful writer and broadcaster, and 34 years her senior.

The two are clearly convinced that they have found a great love, but from the very beginning Hans seems more like a teacher than a lover to Katharina. As time goes on he becomes violent, punishes her severely for a brief betrayal and tries to re-educate her into submission. The dark nature of their relationship finds expression in Erpenbeck’s characteristically unyielding style. The novel is written in the present tense, a technique that can be flattening when used by lesser writers. In an elegant translation by Michael Hofmann, here it creates a claustrophobic intensity. Erpenbeck’s ability to make you enter so completely into the obsessive nature of the lovers’ experience is disconcerting, and as Hans becomes more and more cruel, it is increasingly uncomfortable. As Katharina is ground down by him, the reader suffers along with her, page by page, longing for her freedom.

Anyone who has read Erpenbeck’s previous work will know that she is not committed only to personal stories. She grew up in East Germany, and her novels are always the stories of Germany, its politics and history, as much as they are about their protagonists’ private lives. In Go, Went, Gone, published in English in 2017, she dramatised the experiences of refugees newly arrived in Germany alongside the tale of a retired professor whose own sense of home had been rocked by the fall of the Berlin Wall. In The End of Days, published in English in 2014, she gave her protagonist a number of different lives, buffeted by political cross-currents towards different deaths.

Kairos is the apotheosis of this endeavour to fuse the personal and the political, as our two lovers experience and sometimes seem to embody the political reality of East Germany at the end of the communist dream. The relationship finds wider echoes in that country’s lost ideals and its insistence on holding on to the past long after its inhabitants know they must move on.

Take the moment when Hans, while working on a book about his country, discovers a note in which Katharina has written down evidence of her infidelity. “In February 1956 Khrushchev speaks for the first time about Stalin’s crimes. In March 1956 Brecht falls ill, in August he dies. The Stalinallee in Berlin is renamed Karl-Marx-Allee. Someone picks up the disdained name and throws it over a low wall into the adjoining yard … There are three weeks between the night Katharina spent in the studio and the day where she hurries out to buy some cake, while Hans is ferreting about for an empty bit of scrap paper … He finds one, but it has some writing on it.” So Hans is reliving the way the Soviet Union could not cover up its lies at the moment he uncovers Katharina’s lies, and remembering Brecht’s despair just as he is about to despair over Katharina’s betrayal. Yet there are no exact parallels here, and the gaps that emerge between the personal and the political feel just as important as the closeness.

Once the Berlin Wall falls, the relationship begins to change, and the inertia that had held the lovers in one another’s orbit for so long loosens. Gradually, Katharina moves on, but that is not to say the book has a happy ending. As western values prevail, “the freedom to consume seems like an india rubber wall to her, separating people from any yearnings that might transcend their personal and momentary wishes. Is she about to be another customer?”

This suggestion that even outside such a destructive relationship, there is no emotional fulfilment available in our depleted world is a deeply troubling one. Katharina’s final discoveries about the past reveal yet more unanswered questions about her relationship and her times. Throughout these personal and political journeys, Erpenbeck never reaches for the stock phrase or the known response. While the novel is indeed bleak in its view of love and politics, spending time with Erpenbeck’s rigorous and uncompromising imagination is invigorating all the way to the final page.

• Natasha Walter’s next book, Before the Light Fades: A Memoir of Grief and Resistance, will be published in August by Virago. Kairos by Jenny Erpenbeck, translated by Michael Hofmann, is published by Granta (£16.99). To support the Guardian and Observer, order your copy at guardianbookshop.com