Set in the fictional war zone of Borogravia, Monstrous Regiment details the struggles of a bunch of raw recruits, veterans and vampires, a la The Dirty Dozen and Band Of Brothers. Or rather band of brothers and sisters, because although Terry Pratchett's latest Discworld hardback best-seller is about the futility of war, it touches more on the battle between the sexes. Yes, the undisputed king of satirical fantasy has gone all gender-specific on us. Pratchett is suffering from flu, forcing him to abandon his book signings and personal appearances, which is as big a turn-up for the book - if you can forgive a pun being turned on its head - as him discussing gender roles. Pratchett is famed for attending almost anywhere to sign copies and give talks, be it at Discworld conventions or bookshops in the United States and Britain, his two primary markets, according to his Doubleday publicist Pru Jeffreys. Such promotion helped him achieve 6.5 per cent of all hardback sales in Britain in 1998. A dozen titles at least have reached the No 1 spot. While poignant and funny - Pratchett is never dull - the book is darker than most of its 30-odd Discworld predecessors. As one reviewer put it: 'Monstrous Regiment is more a serious novel that also makes you laugh a lot than a comedy that has serious bits.' 'It depends on what reviewers mean by dark; they said it about Night Watch too, by the way,' says Pratchett. 'It is a book about a nasty, bloody little war, and that influences the humour which is, I'd say, closer to that of M*A*S*H. Discworld contains more than 30 books now, and the reason it has stayed successful is that it's changed and evolved.' Did the lead-up to the Iraq war have much of an influence? 'Not really, the world has had a more than adequate supply of stupid, pointless wars,' he says. So why, after 30-odd books, does Pratchett discuss gender roles now? 'The book is, initially, about Polly's search to find her brother and the means by which she does it. She doesn't start out with any particular agenda because she's never experienced anything other than the old-fashioned society in which she lives. To her, old-fashioned society is normal. She starts with clear, selfish personal goals, and then finds out that these can't be achieved without changing the whole of society. I'd say the book is as much about the 'politics' of people in general as it is about gender, but as for 'why discuss it now?' - why not?' Did he find it difficult writing a book from a young woman's perspective? After all, he is a man and, at 55, far from young. 'On specific details, yes. But I also did a lot of research on women who've gone to war disguised as men [as many as 1,400 of them in the American civil war, for example]. They did it for all sort of reasons and many of them were good enough at it that only death or serious injury gave them away. 'The fact is that in a society like that in, say, most of the western world in the early 19th century, a clever woman could pass as a man for years. Men are easy to fool. 'It was really all down research and thinking about how real people act and think. Polly is, after all, a soldier as well as a woman, and she starts to think like one. It was interesting to find her trying not to despise the downtrodden women who, as she sees it, hadn't taken the short-hair-and- long-pants road to freedom.' It may seem odd that a male writer of fantasy, a genre lapped up by pre-pubescent boys, is talking about female equality - or perhaps not: Pratchett's audience is largely female, with 60 per cent of it, he admitted recently, aged over 25. Now that is a real turn-up for the book.