Hay Festival 2012: Terry Pratchett Sir Terry Pratchett has a T-shirt that he's rather proud of. "How to be a fantasy writer," says the slogan. 1) Write an excellent story with a complex plot and great characterisation. Include social and political commentary, touch on such subjects as the nature of belief and journalistic freedom. 2) Put in one lousy dragon. Pratchett is, after JK Rowling, the most popular novelist in Britain. He has written more than 50 books - the 51st, The Long Earth, comes out this month - that have sold more than 80 million copies. Yet commercial success has not been matched by critical acclaim, with only a few members of the literary establishment, such as AS Byatt, seeing beyond the "fantasy" label to evaluate his work on its own merits. More recently, the "embuggerance" of a diagnosis of posterior cortical atrophy - a rare form of Alzheimer's - and Pratchett's emergence as a doughty campaigner for assisted suicide (and presenter of a moving and award-winning documentary on the subject) have ensured that the people have focused as much on what he says as what he writes. This isn't just a shame, it's an injustice. Over the years, without many people noticing, Pratchett has created one of the most imaginative and fully realised fictional universes in modern literature. It would be tempting to compare it to Wodehouse's world of Eggs, Beans and Crumpets. Except that Pratchett's Discworld isn't frozen in amber, but the product of decades of vital and violent evolution. Given that many people will have picked up a Pratchett at some point, the conceit needs little elaboration. Somewhere in space sits a pizza-shaped world, rotating on the back of four elephants, who in turn stand on the back of a giant turtle (occasionally cocking their legs to let the spindly Sun fly past), as it swims its way through the cosmos. Originally, this was the setting for straightforward - if beautifully sketched - swords 'n" sorcery pastiche, featuring the cowardly wizard Rincewind and his omnivorous, ambulatory luggage. But the fourth Discworld novel, Mort, started to show Pratchett in a different light: this tale of an awkward, gangly lad taken on as Death's apprentice managed to be as moving as it was funny. Soon, he had hit a vein of form unmatched by few British writers. Wyrd Sisters riffed on the witches of Shakespeare, introducing one of the classic literary double acts in the shape of elder witch Granny Weatherwax and her earthy sidekick, Nanny Ogg. Moving Pictures pastiched Hollywood; Guards! Guards! gave the world's spear-carriers their due, and Small Gods satirised organised religion, democracy and Ancient Greece. There was also Good Omens, a collaboration with the then-unknown Neil Gaiman that brought the Apocalypse to suburban England, in a perfect fusion of styles of sensibilities. As a teenager, I was convinced that Good Omens was the funniest book ever written. Yet as the years went by, my passion for Pratchett cooled, whether because I was becoming more mature, or because the production line that brought a new novel every six months appeared to have drained much of the passion and sparkle from his work. On returning to his work later in life, however, I found something delightful: the gagsmith had transformed himself, without anyone noticing, into a satirist. Although he continued to rotate between subjects, he seemed to find himself increasingly drawn to the sprawling city of Ankh-Morpork, which in the course of his recent books has undergone a wrenching process of industrialisation. Modern worries about public services, financial greed, immigration, the disruptive impact of technology: all found an echo on Pratchett's pages, alongside the silly jokes (such as one character turning out to be the Fifth Horseman of the Apocalypse, who left before they got famous), delightfully arcane trivia and the occasional knob gag. The critics might fail to appreciate the results, but the public appears to think differently. An adaptation of Nation, a non-Discworld novel set amid a lost tribe of Pacific Islanders, was a smash hit at the National Theatre. Sky have adapted a series of Pratchett's novels for television, again to strong ratings. His novels continue to sell by the million and is up for the Bollinger Everyman Wodehouse Prize, announced today at Hay. It is might be too far to describe Pratchett as a second Wodehouse: his books are too baggy, loose and idiosyncratic for that. But they have brought great joy to an extraordinary number of people. It would be a shame if their author was remembered only as a campaigner, or a nerdy chronicler of dungeons and dragons, when his work offers so much more. Terry Pratchett is speaking at 5.30pm in the Barclays Pavilion [Event 279]