This is one of the book I frequently use and read all these years. Its a comprehensive book about the science of baking and it cover all the basic terms and steps in baking pastries, cakes and bread. Although I never actually use this book for the recipes but I find it provide wealth of information that you wouldn’t find even in the wikipedia.
The recipes started with the basics to intermediate and professional. Unlike the Professional Cooking where you don’t really need the precise measurement for everything, Professional Baking is a good companion to had for beginners of cooking or culinary students. Hence why the book is rather condensed with basic instructions including introductory to the commonest items used in baking like flour, water, oil but it does provide more information like the type of flour being used in recipes, the 12 steps taken for baking a bread down to the types of chocolate you can make.
It was never a replacement for the actual kitchen work with the chef but if you have a need to know the differences of Italian and Swiss Meringue or the Scottish or French method for laminated dough, this book can help you with the definition and description. Its not a must have for average bakers because of the size of the book and the overall non-specificity of the content. But if you are interested in baking, this book will help you down to the basic.