The “angry letters” have already begun arriving. Philip Pullman’s new book The Good Man Jesus and the Scoundrel Christ will not be in the shops for another two weeks, with its content being kept a closely guarded literary secret.

But some people believe they already know enough to inform the Oxford author of the fate that it will earn him in the afterlife; and it is not a happy one.

“The very existence of the book makes some people cross,” said Mr Pullman, sounding remarkably unruffled. “And they are writing to say just how cross they are. Some say I am going to be sent to burn in hell for eternity. And they are absolutely certain of this. But I think these letters are from the extremist end of the spectrum.”

It is difficult not to admire Mr Pullman’s quiet resolve as he prepares to face a storm of protest and controversy over his new book about the story of Jesus.

By choosing to unveil it at The Sunday Times Oxford Literary Festival, which begins on Saturday, at least the award-winning writer can be sure he will not be short of friends.

The author of the His Dark Materials trilogy has always been one of the biggest draws at his home festival for 12 years, which has somehow often coincided with key moments in Pullman’s writing career.

At his first appearance he spoke about Northern Lights, the book he wrote in the hut behind his Oxford home that was destined to change his life, while two years ago he attracted more than 700 people to the Town Hall to hear him speak about Once Upon a Time in the North, the prequel to the acclaimed fantasy trilogy that many believe puts him up there alongside Tolkien and C.S Lewis.

But even allowing for the excitement stirred by revelations about how the balloonist Lee Scoresby became friends with the armoured bear Iorek Byrnison, his appearance at the Sheldonian Theatre on Sunday, March 28, promises to be a landmark of an altogether different order for Mr Pullman.

For the event will see him speaking in public for the first time about The Good Man Jesus and the Scoundrel Christ, which offers his personal take on the most influential story ever told.

Some advanced stories have dubbed it “an assault on Christianity” which denies that Jesus was divine, challenges the Gospels and argues that it was Paul who transformed the story of Jesus into the version we know in the New Testament.

The publishers, Canongate, say the new book is part novel, part history and part fairytale. So how does Mr Pullman describe it?

“My book is a story about Jesus, told by me from a different point of view,” he replies.

Many people had thought that the novelist had long since grown weary of defending his books against those who insist they carry an anti-religious message and had convinced themselves the brainwashing organisation called the Magisterium could be equated with the Vatican.

It was even widely reported that plans for a sequel to the film The Golden Compass, based on the first book in His Dark Materials trilogy, were put on ice as a result of fervent Christian protests, which sparked boycotts of the movie in the United States. So you do wonder why he is willing to risk again the wrath of the Vatican and established churches, let alone those who take a more hardline position on religious issues. I mean, just think back to the Jerry Springer. The Opera protests.

“Well, I am not afraid of people with banners,” said Mr Pullman. “People with guns, yes, that is something that would lead me to have more fear. But I don’t think anyone was shot after the making of Jerry Springer. The Opera. And I don’t think anyone will be shot after the publication of this book.”

The idea of the book first entered his mind more than six years ago during a conversation on the stage of the National Theatre with Rowan Williams, the Archbishop of Canterbury.

In a discussion about His Dark Materials, the archbishop said he was curious to know why there was nothing about Jesus in the trilogy.

“I thought it was a perfectly good question. The church, as I represented it in His Dark Materials, is a sort of Christian church. So why no mention of the central figure?”

He told the archbishop he was right, and he would deal with Jesus later in another book.

The perfect opportunity to keep his promise came with an invitation to write a book for Canongate’s The Myths series, with a number of leading writers invited to retell a myth in a contemporary way.

But does that not now mean that a man who has always insisted that he was “a storyteller and that’s the beginning and the end” is now destined to be bracketed with Richard Dawkins and other ‘militant atheists’?

He objects to the word ‘militant’ being applied to Richard Dawkins, the best-selling Oxford author of The God Delusion, who will also be appearing in the Sheldonian Theatre during the festival, talking about ‘Science, Certainty and the Royal Society’. Suicide bombers and those urging beheadings are the militants, he insists.

“Richard Dawkins is forceful in putting forward his arguments. But I would not expect to be bracketed with anyone in particular. But that is not something in my control.”

In any case, Oxford’s two best known atheists belong to different worlds.

“What Richard Dawkins is doing is arguing lucidly from a position of scientific knowledge and I respect and admire that very much. I have very little such knowledge and I’m not arguing in that way. What I am doing is telling a story.”

Another Oxford academic, greatly admired by Mr Pullman, the Jesus expert Prof Geza Vermes recently suggested in this newspaper that Mr Pullman would be wise to leave the study of the historical Jesus to historians and philologists.

But that is to misunderstand his intentions, says Mr Pullman.

“I have read Prof Vermes’s books and found them enlightening. But I am not in the position of a historian or theologian examining the evidence. That is not what I’m doing. What can a storyteller tell us about really happened?”

But the strength of his feelings about religion is evident: “Religion has many effects, some good.

“But one of the bad effects is that it provides the perfect excuse for people to behave with enormous cruelty and inhumanity.

“All they need to say is, ‘God told me to do this’, and there is no argument and stonings and burnings are done in his name.” He steadfastly ignored the fuss his new book would cause while writing it. “Objections of people and possible widespread interest are minor factors when I’m thinking of writing a book.

“As far as this religious business is concerned, I do have to keep explaining all the time. But over the last ten years I have written other books. People, however, do not argue about those.”

I wonder what the hundreds of thousands of readers who consumed the books about the young girl Lyra, who moves from Oxford to a parallel universe, will make of The Good Man Jesus and the Scoundrel Christ.

While insisting he has never taken any readers for granted, an approach he urges on all authors, he accepts that the Sheldonian Theatre will be predominantly made up of adults.

“I think it will be of more interest to people who know the Bible. I’m taking the story of Jesus and telling it from a different angle. Unless you know the story in the first place that is not easy to relate to.

“The problem is that so few people know the Bible stories. When I was a child it was part of what was all around you, it was part of the atmosphere. Somehow everyone knew the story of the Good Samaritan and the birth of Jesus.

“You cannot assume that any more. I regret that in the same way I regret people not knowing the story of Troy. They are part of our culture as human beings and not just in Western Europe. It is right to read stories from other cultures. The greatest stories all tell us something about what it like to be human.”

Earlier, he told The Bookseller magazine: “I am not setting out to rival the Bible, and I hope my book is not going to cause anyone to slaughter anyone. It is about how stories become stories, and how they become fixed and settled and different from the events they are based on.”

His grandfather was a clergyman in Norfolk and he talks about the King James’s Bible and the 1662 Book of Common Prayer with the deepest affection.

“They made me what I am. You could not cut them out any more than you could cut out a single nerve. They are part of my being.”

The Sheldonian appearance will be only the first of a series of engagements about the book across the country, one being a discussion with the former Bishop of Oxford, Richard Harries.

He accepts that the book will further delay The Book of Dust, the eagerly awaited companion novel to the His Dark Materials series.

“I have it here. My hand is on the manuscript. But it is going to take another two years. Yes, I long to get back to it. But there has been the film, now this book. They have all in a way been distractions.”

His diary looks to be particularly full next week, with a total of five appearances at the Oxford Literary Festival, with The Oxford Times again the local sponsor.

Mr Pullman, 63, who lives just outside Oxford, always claimed his skills as a storyteller were developed while working at Marston Middle School. But one of his most passionately held beliefs is that love of language and stories should be developed in young children long before school.

“The best way to do it is through nursery rhymes. You know I’m almost prepared to stand for Parliament as the candidate for Nursery Rhyme Health.”

My guess is that a spell in Parliament would seem like a welcome break from the pressures of being somewhere between the New Testament and The Book of Dust.

  • Tickets for The Sunday Times Oxford Literary Festival can be bought by contacting the box office on 0870 3431001. The festival website is oxfordliteraryfestival.com