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Ian Stewart
Ian Nicholas Stewart FRS CMath FIMA is a British mathematician and a popular-science and science-fiction writer. He is Emeritus Professor of Mathematics at the University of Warwick, England. --Wikipedia
Darwin's Watch
Charles Darwin, in Roundworld, is hesitating. History has taken a wrong turn — he is writing a book on theology instead of evolution, and the natural selection that should have happened is in danger of not happening at all. The wizards of Unseen University must travel back into Roundworld's past and find a way to get Darwin back on track without changing history too visibly. The third Science of Discworld book, examining the history of evolutionary theory.
Darwin's Watch (The Science of Discworld III) uses Charles Darwin as the focal point of both its fiction and science sections. The narrative explores what might have happened if Darwin had not written On the Origin of Species, while the science chapters examine evolutionary theory.
Terry Pratchett, Ian Stewart, and Jack Cohen. Published in 2005 by Ebury Press.
Recommended. The Roundworld concept and the wizard characters are established in book one, and each subsequent volume builds on it.