Concurrent simulation is over twenty years old. During that pe- riod it has been widely adopted for the simulation of faults in digital circuits, for which it provides a combination of extreme efficiency and generality . Yet, it is remarkable that no book published so far presents a correct and sufficiently detailed treatment of concurrent simulation. A first reason to welcome into print the effort of the authors is, therefore, that it provides a much needed account of an important topic in design automation. This book is, however, unique for sev- eral other reasons. It is safe to state that no individual has contrib- uted more than Ernst Ulrich to the development of digital logic simulation. For concurrent simulation, one may say that Ernst has contributed more than the rest of the world. We would find such a claim difficult to dispute. The unique experience of the authors con- fers a special character to this book: It is authoritative, inspired, and focused on what is conceptually important. Another unique aspect of this book, perhaps the one that will be the most surprising for many readers, is that it is strongly projected towards the future. Concurrent simulation is presented as a general experimentation methodology and new intriguing applications are analyzed. The discussion of multi-domain concurrent simulation--- recent work of Karen Panetta Lentz and Ernst Ulrich---is fascinat- ing.