As we approach a new century, modelling through new mathematical insights and powerful computers grows apace. John Casti has written a truly important book. - The Sunday Times (London). As a popular account of the enormous change computers have brought to the everyday practice of science, it is an easy and enjoyable read. - Nature. Would-Be Worlds gives a spectacular view of this new intellectual landscape. - New Scientist Acclaimed popular science writer John Casti takes us on a fascinating romp through the remarkable simulated worlds being fashioned from the bits and bytes of computers. A new generation of technological marvels now enables scientists to recreate lifelike computer models to better everything from traffic patterns and the stock market to weather systems and the working of human brains. JOHN L. CASTI, PhD, (Santa Fe, New Mexico) is a resident researcher at the Santa Fe Institute and a professor at the Institute for Economics, Operations Research, and System Theory at the Technical University of Vienna. He is the author of Searching for Certainty, Paradigms Lost, Complexification and Five Golden Rules (Wiley).