Suzi Feay: Narnia is like a narcotic - but can the magic be captured on film?

I don't remember the time I first went through the back of a wardrobe into a snowy wood and met a fawn with an umbrella standing under a lamppost. The Lion, the Witch and the Wardrobe was not so much a reading experience as a narcotic one. It had to be repeated, again and again and again.

Bookish children born since 1950, when the first episode came out, have all been Narnians. Francis Spufford, in his memoir of childhood reading, The Child That Books Built, has described wonderfully the drug-like effect of Narnia. Can this magic – derived from such rich ingredients as Arthurian chivalry, Christian symbolism and the Arabian Nights – be captured on film?

The fear for enthusiasts is that the chronicles will be reduced to a bland fantasy: glamour but no grit. We could lose certain unpleasant eccentricities of Lewis's own, which mar the adventures. There are the swarthy, evil, turban-wearing Calormenes who worship a demon and look suspiciously like Arabs.

The children's author Philip Pullman has railed against Lewis for his seeming distaste for adult sexual maturity.But Lewis's misogyny, if that's what it is, had a positive side: he created marvellous female monsters, from Jadis the witch-queen to the serpent-enchantress of The Silver Chair.

Spufford notes the crudity of Lewis's attempts to make children laugh at the victims of his own prejudices, such as the awful Eustace Scrubb whose parents are – how ludicrous! – vegetarians.

Will the film makers attempt to expunge the overt Christian message in the books? From the early 1930s, Lewis had returned to his Christian faith under the influence of his great friend J R R Tolkien and had embarked on a broadcasting and writing career as proselyte, pundit and propagandist. This got up people's noses and certainly irritated Tolkien.

The figure of the faun, Tumnus, complete with umbrella, had haunted Lewis since his teens, but it wasn't until after he wrote the fantastical Screwtape Letters (1942), in which Christianity is seen from the Devil's angle, that he found out how to expand this startling image into a story. Once he started, the other Narnia books followed at a rate of one a year, ending with The Last Battle in 1956. Less than 20 years later, when I was first exploring Narnia myself, they had the air of classics.

Given that The Lord of the Rings and The Hobbit first reached bestselling status with their 1965 imprints, is it fanciful to suggest that Lewis was John the Baptist to Tolkien's greater talent, and that on the campuses of the 1960s, the first generation of young Narnians was looking for new lands to explore?