This book is an exceptionally well-written description of the AS/400. It describes in some detail the internal architecture of both hardware and software. It explains the reasons behind design decisions. Though not a comic strip it contains helpful diagrams to assist the explanations. The AS/400 contains revolutionary concepts not yet found in other less advanced operating systems. It has demonstrated its ability to adapt and coexist with new and superficially rival technologies. Anyone who wants to understand what a real engineer does, to get major insights into and inspiration for software and hardware design cannot afford to ignore this book. To describe it as 'trash', as one reviewer has, is a reflection on the reviewer, not the book.