In the Tripoli of 1979, nine-year-old Sulaiman considers the origins of mulberries. They are, he decides, "the best fruit God has created", and imagines young angels conspiring to plant a crop on earth when they hear that Adam and Eve are being sent down there as punishment. This could be simply a charming piece of whimsy invented by a child – but the time and place in which Sulaiman imagines it reconfigures the story into a tale of dissidents (angels) and exiles (humans).

Sulaiman – whose adult self is the narrator of In the Country of Men – is himself the son of a dissident, Faraj. His family lives on Mulberry Street, along with the families of Ustath Rashid (who is arrested prior to the start of the novel for treasonous actions) and Ustath Jafer (a government official). The street was named for an orchard of mulberry trees, but now only one tree remains – in the garden of Ustath Rashid.

Of course, no tale of heaven and earth can be complete without acknowledging the third player. Sulaiman brings him into the story thus: "God knew of course, he's the Allknowing, but He liked the idea and so let the angels carry out their plan." In the novel, the figure of the Almighty is called not God but – close enough – Guide. "The Guide" is Colonel Gadafy who, Godlike, remains unseen but ever-present throughout this haunting debut of growing up in a world of uncertainty.

One of the book's most satisfying and moving aspects is Hisham Matar's decision to make uncertainty manifest itself to Sulaiman through the figure of his mother, Najwa. At nine, Sulaiman is able to remain relatively unaffected when Ustath Rashid, the father of his best friend, is taken away in a white car. He even finds himself somewhat drawn to the figure of Sharief, one of Rashid's abductors, who later takes to watching Sulaiman's own house when Sulaiman's father falls under suspicion of treason. But he cannot be unaffected by his mother, who starts taking copious amounts of "medicine" – sold to her by the baker in brown paper bags from under the counter – each time her husband is away (engaged, as she knows, in subversive activities). Under the effect of alcohol Najwa tells her son things she would never say when sober, revealing how she herself was crushed by authority when, as a 14-year-old girl, she was married off to a man more than twice her age after being seen holding hands with a boy in a coffee shop. What makes Najwa's tale distinctive is the fact that her laments stem not from a lack of care for her husband, but rather from the fact that his anti-state activities put him constantly under threat of discovery by the Guide's men. This is the other side of a dissident's life: the price paid by the family, who must live with fear at all times.

Away from his parents, Sulaiman's world is made up of the neighbourhood boys. But here, too, politics is never far from the reader's thoughts, even if the boys themselves aren't fully aware of how the state impinges on their childhood games. The boys are sons of governments officials or of dissidents – their parents are connected in a web of arrests, favours, confessions and betrayals. And as the neighbourhood games grow darker, Sulaiman learns about betrayal, violence and shame at first hand.

Ultimately, this is a novel most concerned with relationships between people – friends, spouses, comrades and, particularly, parents and their children. Matar movingly charts the ways in which love endures in situations of great repression, but also shows how repression threatens everything, even love, putting relationships under a strain that can be unendurable.

And whatever his subject, Matar writes beautifully. In describing the world of seas and mulberries he is a sensualist; when writing of executions and arrests he is a nuanced observer with a gift for conveying both absurdity and raw emotion. His description of a public execution is an exceptional piece of writing – he is not afraid to bring in details that seem entirely incongruous with the setting, yet serve to give it an air of greater verisimilitude. A man trying to resist being taken to the gallows reminds Sulaiman of "the way a shy woman would resist her friends' invitation to dance, pulling her shoulders up to her ears and waving her index finger nervously in front of her mouth". The scene is by turns absurd, painful and terrifying – and, with consummate confidence, at the crucial moment of the hanging Matar is able to step back from the detailed descriptions and evocative imagery to tell us, simply and chillingly: "Everybody seemed happy."