This is indeed a reference book of the most utilitarian kind. Wondering how many transistors are on an Intel 8088 compared to a Pentium? Can't remember which pins are ground on a 72 pin SIMM? What are those IBM printer control codes? It's all here in Mueller's compact guide. If for some reason you don't find the answer in this book, a chapter describes all of IBM technical literature in detail and how to order it. Another chapter explains how to track down vendors and bulletin boards for further arcane details. Not for the lighthearted, this resource is for serious computer technicians and doctors; my only complaint is not with the content but is compact size and tight binding.