This book is perhaps the best book available about "how steam locomotives work". It is not simply keeping its promise for those seeking the answer to that question but is also a pleasure to read for those who actually do know how they work. You don't have to know much physics. All you have to know is explained in a substantial but easy to understand manner. It is not a dry collection of facts; instead - as said before - it is a book you can also read to enjoy. The authors know the matter and are not leaving any issue concerning the steam locomotive. Drawings, diagrams and photos provide facts and examples for better understanding. The basic concern, when not a basic part of the locomotive or commonplace all over the world, are the concepts used in Great Britain. But the principles of such things like feed-water-heating, which were not widely spread in Britain because of the loading-gauge, are at least mentioned if not (like most of the time) described in detail (though some things may be, well, let's say a little bit inaccurate, e.g. the description to the picture of the "Baureihe 42" - a "Kriegslokomotive" of the german railways - can easily be misunderstood in such a way, that these locomotives made up the major part of the vast buildup of german locomotives during World War II; in fact they played just a minor role as there were built "just" several hundred against the thousands built of the "Baureihe 52" (the rate is about 1:10)). Well, sometimes one would wish to get a more detailed description of some constructions, but, to be honest, this is actually not of concern. The book's issue is to explain the basic principles of the steam locomotive. And this is done fabulously.