Terry Pratchett has finally taken us to the far side of Discworld. At the end of Interesting Times, Rincewind found himself on a red-soiled beach, confronting four black-skinned blokes who offered him a gift - a painted, strangely bent, stick. Disgusted with such a tainted offering, the failed wizard threw it away . . . We never find out if the boomerang actually returns to bash our hero, but he's obviously in a land new to his experience. The Four Ecks continent could be described as the world upside- down. Except that's impossible on the Discworld and hemisphere-centric on ours. The trees shed their bark instead of their leaves and an amazing number of animals have pockets. The place is dry, dry, dry. In fact, it's Rincewind's destiny to bring the current drought to an end. He's informed of this by a animal with a face like a rabbit, but with legs that can disembowel you. The kangaroo talks, but he's a hopping thesaurus of body language. Rincewind, of course, flees. There are many places he can go, such as Dijabringabeeralong. The Last Continent "isn't about Australia, it's just vaguely Australian." Pratchett's knowledge of the model for Four Ecks is astonishing in its breadth. We share it through his captivating prose and engaging wit. Our first encounter with Rincewind is while he's seeking a meal. "Grubbing for grub" in "the Bush" can only mean one thing. Rincewind's soliloquy dances around the identity of a major Outback protein source without ever actually naming it. Later, Rincewind encounters the memory of Tinhead Ned, meets someone named Clancy who's a wealth of Four Ecks homilies, and brews up a foodstuff known in the UK by another name. But any school child in the model for Four Ecks knows it intimately, because Vegemite is a staple there. While Rincewind is fleeing from a destiny he fails to understand, the Wizards have an adventure of their own. This lightly attached second plot provides Pratchett with an opportunity for more serious matters. Having disrupted the flow of time, the Wizards find themselves on an isolated island. Strange events occur - the emergence of cigarette trees, an inordinate number of beetles crawl and flit about. The most bizarre of all is the toga'd figure who appears and seems to be the cause of all these manifestations. And well he might, he's a god. Unlike all other gods, he urges his followers to ask questions, to challenge whatever is "established" and to see change as normal. He uses the world's smallest screwdriver in tinkering with his creations. He's the god of evolution. Pratchett's research in this area shows him at his best. He knows that for millions of years life on this world multiplied without sex. When evolution produced sex, life changed forever. A recent spate of books on the evolution of sex shows how challenging the research can be. Pratchett's hilarious presentation in this book could lead you to believe he's read every one of them. It's a superb effort of scholarship, delivered in a way that only PTerry can provide. It would be enlightening to wander into his study and view his reading collection. Those who grizzle about this book are either unaware of the models he uses or are challenged by the fact that Terry is not always "just funny". Many of his books relate the tale with some deep, serious undertones. Pratchett's one-liners are among literature's best. His characters are stunning outtakes on people we encounter daily, sometimes to our distress. But he's a wise, caring man who, as a clever writer, deals with a full range of issues. That the Discworld "is a mirror of worlds" should be taken seriously. If you're looking in that mirror and don't like what you see, you'd better look a little harder. Perhaps something in the image needs adjustment.