The film is powerful but needlessly stylised, Morris using actors to recreate the scenes of the photographs. Gourevitch's prose, by contrast, is spare and unemotional, letting the voices of the soldiers dominate. 'I wanted not to get between the reader and the material,' he says. 'I didn't feel the need to supply outrage or judgments all the time.'

The Bush administration portrayed the Abu Ghraib fiasco as the misconduct of aberrant rogues, or 'seven bad apples', rather than a result of American policy. But Gourevitch shows how, by eroding the applicability of the Geneva Convention, it created the legal vacuum that facilitated the abuses. The low-ranking soldiers were ill-trained, with few resources, and instructed by their superiors that brutal torture was standard operating procedure.

'These young volunteer men and women walked into the prison and found themselves put in a position that was completely untenable, with a corrupt and largely illegal policy in place,' he says. 'They were made into instruments of a great injustice. They were then subsequently subjected to a great injustice when they were made into scapegoats.'

Gourevitch chose not to travel to Iraq, given the dangers. 'By the time that I got involved,' he says, 'Abu Ghraib prison had been shut down. The story as I saw it existed entirely in the voices of these soldiers, who are now all home.'

Gourevitch sees his book as a war story rather than a polemic. 'It's an account of what happened to a group of soldiers who were sent into a prison where this was the policy. It's not a human rights report.'

The infamous snapshots are not reproduced in the book. 'Allowing the words to be heard without the distraction of these images allows you, in a sense, to see again through language and see afresh,' he says.

No image has become more iconic of the atrocities than that of Lynndie England, otherwise known as 'leash girl', holding a strap attached to the neck of a naked inmate. England has often been misrepresented as mentally defective, according to Gourevitch, and she felt the picture was misinterpreted: 'She said that that was a picture of someone being extracted from a cell - it wasn't a dog leash and she had not been tugging on it.'

The only record of moral reflection at the time of the abuses is found in the letters of Sabrina Harman, a lesbian reservist shown in photographs giving a thumbs-up over Iraqi bodies. The letters, addressed to her partner, reveal a deeply troubled conscience. 'She was never an instigator,' Gourevitch says, 'and she was always going out of her way either to avoid the most unpleasant inflicting of discomfort on the prisoners or find ways to offer them comfort.'

The soldiers rarely knew the real names of the detainees, whom Gourevitch refers to by their nicknames. He wanted to protect the prisoners' identities - because the US military estimates 80 per cent of them were never identified with any wrongdoing.

'The only possible effect that publishing their names could have would be to taint them with having been prisoners,' he says, 'which just doesn't seem fair if they're not accused of anything.'

The soldiers were forthcoming in the interviews because they welcomed the opportunity finally to give their version of events. 'During the period when the pictures first came out, the army was holding them pending trial,' he says. 'They didn't have access to the press. So they heard their stories created, as it were; they were public figures in this scandal without having any voice in it.

'They would describe being involved in the events with a candour and directness that was not in their minds self-incriminating, because they were describing not what they felt they'd taken the initiative to do but what they were told to do.'

The book generated more controversy recently when it was revealed that Morris paid several of the interviewees for their time.

Chequebook journalism is common practice in documentary filmmaking but a grave taboo in the print media, where it is believed to encourage subjects to sensationalise their stories.

Extracts from Standard Operating Procedure had already been published in The New Yorker, which strictly forbids journalists to pay interviewees. The magazine's editor, David Remnick, has said he was unaware that the work was based on paid-for interviews. When asked whether he would have run excerpts of the material if he had known, Remnick refused to discuss a 'hypothetical situation'.

Morris suggested to The New York Times that he perhaps should have disclosed the payments in the film, but Gourevitch has no regrets. 'We certainly never made a secret of it. There was nothing in the interviews that suggested the material was compromised. It wasn't a problem for me because he wasn't doing it in the print journalism world,' he says.

Gourevitch didn't turn to reporting until the early 1990s. As a teenager, he decided he wanted to write fiction and took three years off from his undergraduate degree at Cornell University to hone his craft. 'There's very little of what I wrote at that time that was published, but I came out of it really knowing how to handle sentences,' he says.

A master's degree in creative writing at Columbia University followed and freelance book reviewing for weekly Jewish newspaper The Forward led to the offer of a job as New York bureau chief. When Gourevitch mentioned that he had no reporting experience, the editor replied: 'Good, then you have no bad habits,' and signed him on. 'I loved it immediately,' Gourevitch says. 'I was writing a ton of stories each week.'

He moved into freelance work for magazines such as Harper's, Granta and The New Yorker, where he became a staff writer in 1997. Dissatisfied with the media's reporting of the carnage in Rwanda, he spent three months there writing a 15,000-word story for The New Yorker, which he extended into his multiple award-winning book We Wish to Inform You That Tomorrow We Will Be Killed With Our Families (1998). It was followed by a shorter work, A Cold Case (2001), about an unsolved double murder in 1970s Manhattan. Gourevitch returned to fiction in 2005 when he became editor of The Paris Review, once described by Time as 'the biggest little magazine in history'.

The quarterly journal was founded in 1953 for 'the non-drumbeaters and non-axe grinders' by Peter Matthiessen, Harold Humes and George Plimpton, who edited it until his death in 2003.

Gourevitch redesigned the magazine to make it taller, wider and trimmer and began publishing more poems by fewer poets, with portfolios of two or three individual poets in each issue.

'In the old days, the magazine often had 30 or 40 poets per issue and they were sprinkled throughout,' Gourevitch says. 'I always felt that that made them seem somehow secondary and also that it became very hard to get a sense of a poet.'

The magazine's tradition has little influence over his decisions, he says. But he has kept faith with the founders' decision not to publish criticism, believing that it should remain a journal devoted to writing rather than the discussion of it. And he has preserved the tradition of the regular question-and-answer interview format with literary masters, for which The Paris Review is perhaps most famous.

Gourevitch has been editing the interviews, spanning 55 years, into a four-book set, the third volume of which is due out this year. They are not standard newspaper-style interviews, where the journalist-interrogator can catch the author off guard, selectively quote and note hesitations and evasions. They arise out of several long conversations - often across months or even years - and the author is given the chance to revise and polish the transcript.

'We find that the knowledge that you are going to be able to review [the content] makes people more forthcoming and spontaneous because they relax,' he says.

Gourevitch says the process works because writers are interested in the truth. 'It would never work for politicians, who are constantly trying to create a public front and a careful package,' he says. 'Writers are really only interested in trying to present how they are.'

But in an age when authors must become celebrities to sell books, that is a questionable view. Like political reportage, literary journalism requires probing writers like Gourevitch to question the mythologies authors create about themselves: to get beyond the frame.

Writer's notes

Name: Philip Gourevitch

Genre: reportage

Latest book: Standard Operating Procedure: A War Story (Picador; Penguin)

Current project: editing a fourth volume of The Paris Review Interviews

Born: Philadelphia, Pennsylvania

Age: 46

Family: married to New Yorker staff writer Larissa MacFarquhar; one daughter

Home: Brooklyn, New York

Other books: We Wish to Inform You That Tomorrow We Will Be Killed With Our Families: Stories from Rwanda (1999); A Cold Case (2001)

Other jobs: editor of The Paris Review

What the newspapers say: 'Although Gourevitch lets the soldiers speak for themselves, his few analytical forays are invaluable.' - The Guardian on Standard Operating Procedure

Author's bookshelf

The Good Soldier by Ford Madox Ford

'Ford's 1915 masterpiece: 'The saddest story I know,' says John Dowell, the narrator. No story of misplaced love or of dishonour is more perfectly told.'

The Postman Always Rings Twice by James M. Cain

'There's nobody with a better ear for American speech and the swagger of those hurtling towards doom than Cain. The French might not have thought up the existential novel if Cain hadn't showed them how with this one.'

Man's Fate by Andre Malraux

'The most acute political novel of the 20th century. An incisive account of the life of the mind and the life of action coming together to make history ... Malraux is not read so much these days and it is a great loss to the political imagination.'

The Doctor Stories by William Carlos Williams

'Stories written with the swift, concise, unsentimental exactitude of a great diagnostician who also happened to be a great poet.'

My Traitor's Heart by Rian Malan

'His Boer ancestors pretty much invented apartheid and Malan's memoir and investigation of race murders in the last decade of South African minority rule is the most ... intelligent, passionate and excruciating book of non-fiction written in my lifetime.'