I was shocked that I am the first person to review this book because, by now, Prof. Eric von Hippel's book is a classic in the field of research into the causes of innovation. One of von Hippel's key arguments in this book -- as well as in subsequent research and publications -- is that a lot of innovation comes from users of products and services. As users find new uses or new needs for products and services, producers often innovate to meet those needs. While that may seem obvious, this book was one of the first works to verify it in a scientific and rigorous way. Much more surprising than the conclusion just presented is how von Hippel found that users themselves often made the modifications or created new products and processes that lead to innovation. This book belongs in the library of anyone interested in innovation: scientists, engineers, economists, and businesspeople.