Today's computers might seem fast, but their architecture requires that data has a chance to settle down before it is used. If the data could be kept on the move all of the time then they could be even faster. But to do that you need a different way of doing things, such as nonlinear optical devices. That was the sort of thing I expected from this book, together with such subjects as the thermodynamics of computation and digital models of physics. Unfortunately I found that most of the papers were about cellular automata, such as Conway's 'Game of Life'. Now this is an interesting topic research area, and the end results, when displayed on a computer can be fascinating , but I can't say that I really want to know the details of the models - I tended just to look at the pictures.
The beginning of the book made it look like it might have the breadth of coverage I was looking for, with chapters by Toffoli and Fredkin, including their well known 'Conservative Logic' paper, as well as a contribution from Norman Margolus. However, these papers were from 20 years ago, as an illustration of the past of the subject. After that it's mostly Cellular Automata, although chapter 12 'Gated Logic with Optical Solitons' by Blair and Wagner was more what I was looking for, as was Adamatzky's own contribution. But the book's mostly for those interested in how to do computations in cellular automata - if you were interested in Wolfram's 'A New Kind of Science' and want to know more of the theory of computational universality then you should read this book.