Cellular automata machines
The book is based on a dedicated machine for running CA's called the CAM, running a version of FORTH. Nowadays Moore's law means that almost everyone would use a PC for such modelling. I didn't feel that this difference was a problem, rather the details of their machine gave a better idea of what was happening in the CA's and would be valuable for anyone who wants to program CA's themselves. The authors' consideration of reversible CA's and how they can show the consequences of reversibilty of microphysics is also very useful. This is a short book, but covers plenty of topics, and I'd recommend it to anyone considering using CA's to model physical systems.