Once upon a time, the bestselling author Philip Pullman used to entertain his son by recounting tales from the Odyssey each night. Time passed, and by the end of the story the boy was so galvanised that he bit a chunk out of the glass he was sipping.

A few more folk are spitting glass at the unholy prospect of His Dark Materials, the epic trilogy in which Pullman kills off God, being showcased at the National Theatre as a Christmas family show.

After all, the fantastical stories have been condemned by The Catholic Herald as “fit for the bonfire” and their 57-year-old author damned for his “shameless blasphemy” by the Association of Christian Teachers.

But hey, Pullman’s great train of followers are thrilled that his world of witches, armoured bears, angels and daemons is being turned into the National’s most ambitious production in years under the innovative regime of Nicholas Hytner, the theatre’s dynamic young artistic director. A cast of 30, led by Timothy Dalton, Patricia Hodge and Niamh Cusack, are in rehearsals for two plays, each running for three hours.

It is the latest twist in a remarkable personal narrative. Pullman’s progress reads much like a fairy story: years of oblivion as a dreamy schoolteacher scrawling in longhand in his Oxford garden shed, then the explosion of acclaim in 1996 that blasted his books into the select realm of cross-over readership between children’s and adult fiction.

This grey-haired creator of dark forces comes in the guise of a kindly, avuncular figure who lives in chaos and is married to Judith, a former hypnotherapist. They have two grown-up children, one a musician and the other at Cambridge, and two flatulent pugs, Hogarth and Millie.

Pullman’s substitute for religion is watching Neighbours. “There is no distracting realism, the acting is terrible and the characterisation is negligible, so all you are left with is the story,” he explained once. The story’s the thing, in his book. Children don’t want irony or cleverness.

His stories are bursting with big ideas, which is why his moral epic, with two children as its stars, has proved irresistible to Hytner. The director summarised the questions posed by Pullman thus: “Why are we here? Is there a God? If so, why is he indifferent to our welfare.”

The playwright Sir Tom Stoppard has also been spurred into writing the first film script of the trilogy.

Yet the magician who conjures mysterious parallel worlds craves a stable universe. “I want dullness, days and days and weeks and months of solemn monotony,” he insists. Instead, he gets dragged on to Desert Island Discs and The Big Read, not to mention public discussions with the Archbishop of Canterbury and the scientist John Gribben.

The same man takes delight in shocking people with outspoken views on everything from the narrowness of children’s education to the undesirability of the Iraq war. He doesn’t hold back. “If you want to hit someone, hit ’em hard,” he says.

He may have been hailed as a literary genius comparable to Chekhov, Dickens, Blake and Milton, but he has poured scorn on many other children’s authors. He finds CS Lewis’s Chronicles of Narnia “blatantly racist”, Tolkien “psychologically uninteresting” and is no fan of Roald Dahl. However, he loves Arthur Ransome and Noddy.

At the centre of Pullman’s opinionated ferment is his attack on organised religion. Described by its author as “Paradise Lost in three volumes”, His Dark Materials is in fact a reversal of Milton’s tale of the war in heaven. This time God loses out. Lyra and Will, two children from other universes, are recruited to a rebellion against a pathetic deity so that a “republic of heaven” can be created instead.