In this slim but powerful work, David Grossman produces a harrowing testimony to grief, the sort that only those who have lost a child can fully understand.

Written more as a play than as a novel, it reads like a very sombre version of The Canterbury Tales, in which its cast of travellers talk while they walk, though where they are going not even they could say.

Grossman's most recent novel, To The End Of The Land, also took the form of a story that unfolds through a conversation conducted as his heroine Ora and her former lover walk the boundaries of their country. Ora has fled her home in Jerusalem to avoid the messenger she fears might bring news of her soldier son's death. In conversation with her friend, who is also the father of her son, she tells him about their boy, hoping that in doing so she will magically preserve his life.

It is well known that as he was writing that book, Grossman's 20-year-old son was killed in action as part of an Israeli armoured unit in Lebanon. A writer's own story should not influence how one reads his or her work, but in the case of Falling Out Of Time one would not even need to know Grossman had suffered this loss, since every line is alive with pain.

The story opens in a kitchen, where the bereaved husband and wife are talking. The man says he wants to go out and walk "to there". There is no "there" replies his wife and, even if there was, if he reached it she fears he would not return to her. "No-one ever has."

It is five years since their son Uwi died, "five years on the gallows of grief". When they were informed of his death, the husband recalls, "the man and woman we had been nodded farewell".

Even though his wife refuses to join him - "I would go to the end of the world with you, you know. But you are not going to him, you are going somewhere else, and there I will not go, I cannot." - the man sets out and begins to walk around his house, then his town. All the while he talks to his son, revealing the agony of living while he is dead: "A man from far away once told me that in his language they say of one who dies in war, he 'fell'. And that is you: fallen out of time while the time in which I abide passes you by."

As he walks, he slowly gathers a trail of followers, each of whom has buried a child: a netmaker, a cobbler, a midwife, a maths teacher, a town chronicler, a duke.

Grossman is scrupulous in placing his tale beyond borders. The landscape is anonymous, more fairytale than Israel, and the period could as easily be 500 years ago as today.

Formal in tone, like a piece of highly choreographed dance or a deliberately staccato play, Falling Out Of Time is suffocatingly sad. The obvious torments of loss are compounded by those one would never think of: the cobbler who holds 10 nails in his mouth all day, "One for each of her tiny-tiny fingers I used to kiss"; the writer who has become half man-half desk - hence his name The Centaur - who is compelled to write about what happened: "That's the only way I can somehow get close to it, to that goddam it, without it killing me, you know."

And yet, from the depths of torment, this caravan of mourners begins to find a glimmer of solace. At least they now recognise that they are not entirely alone. More than this, however, the husband who opened the story has a revelation of the sort that no-one untouched by cruel death could imagine. It takes only five words to express, but it is startling in its obviousness and profundity, and the way it explains why some wounds never heal.

Written with such simplicity it appears to be speaking directly to the reader, Falling Out Of Time is at times Biblical in its imagery, at others weird and fantastical. Sensual and uncompromising in its evocation of the way death can utterly suffuse the living, the hurt it expresses is at times almost unbearable to read. It's a measure of Grossman's clarity of thought and his theatrical timing that one reaches its end and feels, in some small way, glad to have been in his characters' company however grim the road they travel.