The latest instalment in the Sunday Times-bestselling Science of Discworld series

It is exhilarating to feel yourself immersed in such well-expressed and up-to-date debates... New Scientist The hard science is as gripping as the fiction The Times Entertaining and illuminating New Scientist Fantastic... this is some of the best science writing around today, intelligent and witty, creative and playful... if only science could be taught like this in school, many of us would have paid more attention Fortean Times

Sir Terry Pratchett is the acclaimed creator of the global bestselling Discworld series, the first of which, The Colour of Magic, was published in 1983. In all, he is the author of fifty bestselling books. His novels have been widely adapted for stage and screen, and he is the winner of multiple prizes, including the Carnegie Medal, as well as being awarded a knighthood for services to literature. Worldwide sales of his books now stand at 75 million, and they have been translated into thirty-seven languages. Professor Ian Stewart is the author of many popular science books. He is the mathematics consultant for New Scientist and a Professor of Mathematics at the University of Warwick. He was awarded the Michael Faraday Prize for furthering the public understanding of science, and in 2001 became a Fellow of the Royal Society. Dr Jack Cohen is an internationally-known reproductive biologist, and lives in Newent, Gloucestershire. Jack has a laboratory in his kitchen, helps couples get pregnant by referring them to colleagues, invents biologically realistic aliens for science fiction writers and, in his spare time, throws boomerangs. Jack, who has more letters to his name than can be repeated here, writes, lectures, talks and campaigns to promote public awareness of science, particularly biology. He is mostly retired.