Philip Pullman is a one-man phenomenon. The first writer to win the Whitbread Prize for Literature with a children's book, sales of his trilogy His Dark Materials now top two and a half million, with copies translated into 30 languages. When he appears on public platforms, the event is inevitably sold out. The two-part adaptation of his work to be staged at the National Theatre in London this Christmas has already taken more than a million pounds in pre-performance bookings - a house record. And there is the promise of a film version, scripted by Sir Tom Stoppard. Not bad for an ex-teacher living in Oxford in his mid-50s, with no outstanding commercial success before the publication of Northern Lights in 1996, the first of the sequence of three fantasy novels that have made his name.
His success gives the lie to any idea that we are all, adults and children, part of a steady process of dumbing down. While Harry Potter represents the less demanding side of fantasy, Pullman offers readers a far more challenging but equally exciting read. There are references in HDM to Milton, Blake, Keats, Dante and Greek mythology, not to mention quantum physics and superstring theory. But at other times, the mood changes from the elevated to affectionately nostalgic borrowings from Edward Ardizzone's Little Tim stories, Richmal Crompton's Just William and Tove Jansson's Moomin tales.
The basic plot of HDM is a rewriting of the book of Genesis, with Eve now shown as doing the right thing when she decides to eat the forbidden fruit and so break away from ignorant innocence. She is represented by Lyra, a modern 11-year-old girl living in an Oxford very like the real thing but with a number of important differences. Her Adam is a boy called Will who comes from today's world but is able to cut his way into alternative universes. Up against them is the malignant power of organised religion, pictured as a ruthless, Calvinistic despotism anxious to nip all damaging heresies in the bud. Lyra's parents are little help, with her father close to Milton's Satan and her mother a stand-in for the wicked Queen in Snow White. The children have to rely instead on a collection of benign witches, angels, talking bears, and insect-sized courtiers, not to mention an American aviator, a barge full of water gypsies and an Oxford don fired from her post for discovering secrets intended to stay hidden.
All the characters in Lyra's world possess their own daemons - a visible, accompanying spirit that can turn into any animal shape at will, a severe technical challenge for the actors at the National. When asked what his own daemon might have looked like, Pullman has suggested a magpie. This image is duly reproduced by the wood engraver John Lawrence at the start of Pullman's recently published Lyra's Oxford, a slight but tantalising after-thought to HDM. The magpie is an apt symbol of Pullman's wide range of interests, which go from drawing - he provided all the chapter headings for HDM - to playing the guitar, watching Neighbours and, currently, carving his own rocking-horse. Of HDM, he says, "I have stolen ideas from every book I have ever read." Other moments of inspiration came from films, a Finnish phone directory and from strolling round Lake Bled in Slovenia, where the constant rumble of overtaking skateboarders gave him the notion of the "mulefa", elephant-like animals that use giant oiled seed pods as their means of locomotion.
So how did this big, warm-hearted, generous man, devoted to his wife and two sons, turn into such a critical and popular success? Born in 1946 to an RAF family constantly on the move, he began early as a storyteller, entertaining his younger brother with lurid tales every night after the lights went out. He began writing for real the day he left Exeter College in Oxford - the model for Jordan College in HDM, where Lyra lives as a child - and has produced three pages a day ever since. Working as a teacher, again in Oxford, he was quickly put in charge of the school play, some of which he then wrote. Several of his earlier books derive from these plays, and there were also four novels set in the late 19th century featuring Sally Lockhart - Britain's first unmarried mother detective. Drenched in a Sherlock Holmesian atmosphere, these novels allowed Pullman to revel in the historical detail conjured up by descriptions of contemporary inventions and advertisements, some real, others invented.
His breakthrough arose from lunch with his editor, David Fickling, and Pullman's casual suggestion of rewriting Milton's Paradise Lost for a modern audience. Once launched into the story, everything he most believed in came into play. His conviction of the power of story to transform lives was harnessed to a tale where Old Testament habits of mind are finally vanquished in favour of his own brand of liberal humanism. His curiosity about modern quantum theory linked naturally to a plot where characters move between the parallel universes that some theorists now believe to be a philosophical possibility. His love of Greek mythology became integrated with a powerful warning against the slow destruction of the natural world which we are all part of, both in life and death. His hatred of authoritarianism was personified by two child characters brave enough to stand up to terrible dangers in pursuit of what they know to be right.
There are contradictions too. Pullman is a man of out-size likes and dislikes, and while on the left, is a passionate critic of the Government's policies on the teaching of literacy. Brought up as a Christian by his beloved clergyman grandfather, he depicts all his priestly characters as canting Pharisees or worse. Disliking organised religion, Pullman is still fascinated by the story of the Creation, which many of his younger readers might otherwise have heard little about. After his two young characters finally fall in love with each other, he then makes it impossible for them to stay together, since each must return to their own world.
But it is not the theological arguments and occasional quirks that probably most attract readers. His powerful trilogy touches on the great issues common to all human imagination. Eternal oppositions such as love and hate, loyalty and betrayal, life and death, truth and lies, courage and cowardice are common themes in the experience of his main characters. In epic style, these leave the security of home in the quest of something far greater than themselves whatever the danger - a plot as old as Beowulf, but as resonant as ever. Stories have always had the capacity to show us the best as well as the worst of ourselves. This particular one, told by a master drawing on skills and experience built up over years of patient apprenticeship, proves irresistible on the printed page, not to mention any future triumphs on stage or screen.
The writer is author of 'Darkness Visible. Inside the World of Philip Pullman', Wizard Books, £6.99. 'His Dark Materials' Parts I and II opens on Thursday at the Olivier Theatre (020-7452 3000)Reuse content