THE pull of the pilgrimage seems to be hard-wired into the human psyche. People have always gone on journeys in search of spiritual enlightenment. And if ever an experience was all about the journey rather than the destination, and the encounters along the way rather than the end, this is the pilgrim's raison d'être.

So it is hardly surprising that pilgrimage has provided such a rich seam of material for the storyteller, from The Canterbury Tales to The Pilgrim's Progress. Surprisingly, perhaps, pilgrimage is as popular as ever, to the point where some famous routes are becoming unappealingly crowded.

The Unlikely Pilgrimage of Harold Fry, then, treads in well-trodden footsteps, and at the same time is very "now" in its appeal. A first novel, it began life as a radio play, written in tribute to the author's father, who was dying of cancer, and taps into the yearning for something, at those periods of profound emotion which are an inescapable part of the human condition.

The title made it on to last year's Man Booker long-list, and became a bestseller, and it is not hard to see why. A sweet and moving story - which avoids being saccharine by virtue of the author's sharp ear for dialogue - it clearly resonated with huge numbers of readers.

The story opens when Harold Fry, a timid man who has recently retired from an unremarkable career, receives a letter from a former colleague, Queenie, who writes that she is dying of cancer. Distressed, Harold writes an inadequate letter of condolence, and sets out for the postbox.

In the event, rather than post it, he just keeps walking - all the way from his home in Devon to the hospice in Berwick-upon-Tweed, where she lies dying. This is partly as a result of a conversation with a girl in a petrol station, who says: "You have to believe. That's what I think. It's not about medicine and all that stuff. You have to believe a person can get better. There is so much in the human mind we don't understand. But, you see, if you have faith, you can do anything."

Not religious faith, she clarifies, just "trusting what you don't know, and going for it". This becomes a touchstone for Harold: although ill-equipped, he phones the hospice, and then sends Queenie the first of many postcards, telling her that he is on his way, and begging her to hang on. He believes that his act of walking will keep Queenie alive.

The journey turns out to be transformative. Harold's encounters as he walks with an array of fellow-travellers change his entire outlook. He meets the unexpected kindness of strangers, and hears extraordinary stories of other people's lives, as they unburden themselves. When he bumps into a journalist, before he knows it a host of unwanted companions have tracked him down in order to join him on the road. An ill-assorted community of modern-day pilgrims springs up, alternately supporting one another and bickering. Harold's private journey becomes appropriated by others, and he finds himself caught up in a media circus.

Most poignantly, the day he set out for the post, he left his wife Maureen busy vacuuming (something she does with peculiar determination). She is left furious, at first, and then bewildered by his journey, which is, to say the least, as "unlikely" as the title suggests. The layers of an unhappy marriage are gradually unpeeled; and, as Harold progresses northwards, Maureen travels on her own journey of discovery.

Each looks back over the small disappointments and greater grief that have led from the promising early days of their relationship to the desperate loneliness of the present, and each wonders whether there is any way back.

Only at the very end of the book do we discover the unfinished business between Queenie and Harold. (A publican tells him: "We've all got things we wish we'd done, or hadn't. Good luck to you. I hope you find the lady.")

Yet, although compelled to continue, even Harold struggles to articulate what drives him; and, as he comes towards the end of the journey, his fumbling sense of purpose begins to unravel. What did he think he was achieving, he wonders, and was it all worth while?

In the end, of course, it turns out that the true gift of the pilgrimage was something that neither Harold nor Maureen (nor the reader) could have expected on the day he left home. And, as Maureen says, "You got up, and you did something. And if trying to find a way when you don't even know you can get there isn't a small miracle, then I don't know what is."

The Unlikely Pilgrimage of Harold Fry by Rachel Joyce is published by Black Swan/Transworld at £7.99 (CT Bookshop £7.20); 978-0-552-77809-1.

The Unlikely Pilgrimage of Harold Fry - Some questions

"There are biblical overtones and elements of parable to Harold's story" (Natasha Tripney, The Observer, 6 January). How far do you agree?

This is Joyce's first novel. Previously she has written extensively for radio. Do you think this shows in the style in which the novel is written?

Harold's passing encounters become significant for him. Have you had conversations with strangers that have remained with you, and made an impact on your life?

"He wished he had not grinned the night his son jived." How do Harold's regrets affect him?

In a message that Harold leaves for Queenie, early in the book, he says: "Tell her Harold Fry is on his way. . . I am going to save her, you see." Where is salvation found in this novel?

"The abundance of new life was enough to make him giddy." How did Harold's journey help him to see the world with new eyes?

How did Harold's journey change his relationship with Maureen?

How did Harold respond to the attempts to make him a star?

What part is played by the countryside in Harold's story?

IN OUR next reading-groups page, on 6 September, we will print extra information about the next book. This is Burying the Typewriter by Carmen Bugan. It is published by Picador at £9.99 (CT Bookshop £9 - Use code CT635 ); 978-1-447-21084-9.

Author notes

Carmen Bugan was born in Romania in 1970, and suffered with her family under the reign of Ceausescu. In 1989, she emigrated to the United States, and studied literature and psychology at the University of Michigan, later gaining an MA at Lancaster University and a doctorate from Balliol College, Oxford. She has written two collections of poems, and has contributed to a range of literary publications. She now lives in Geneva with her husband and son.

Book notes

Bugan's father was a minor political dissident in Ceausescu's Romania. He wrote and distributed leaflets on an illegal typewriter, which he buried in the garden each night. He escaped censure until March 1983, when he held a one-man protest against the regime in Bucharest, and was arrested and sentenced to ten years' imprisonment. Bugan was 12 at the time. Burying the Typewriter is her memoir of a childhood oppressed by the Securitate, and the effects that her father's arrest, and later release, had on her family.

Books for the next two months:

October: Unapologetic by Francis Spufford

November: Toby's Room by Pat Barker