'In this excellent monograph, Marjorie Senechal ... gives us insight into what happened when established ideas had to be reexamined, modified or overturned ... Her several published reports and this book convey both the searches for new directions and the excitement of new results and are worthwhile narratives of ten exciting years.' Science 'This is a little gem of a book, with a quasicrystalline elegance to it.' American Scientist '... this is a nice, timely and valuable book and is recommended to anyone interested in learning about this subject.' European Mathematical Society Newsletter