Author Glynn C. Williams has a great reputation in the world of SAP Sales and Distribution. He has vast experience in the SAP SD domain with a perspective that is helpful for both technical and functional resources. Many people treat this book as a Bible and for someone new to SAP SD, this is not an exaggeration by any means.
The most important aspect of the book is its practicality. It is largely a handbook rather than a textbook. Though divided into chapters which are easy to navigate and are largely in sync with certification materials, the focus has been kept on writing the book in a way a user can make most of it while implementing SAP SD. In short, this book is not an ideal preparation material for certification but a great book to have it an office desk.
Topics are carefully deconstructed to help the user understand the process and steps to implement. For example, creating a Sales Order is explained as a part of the entire process, followed by detailed explanation of each field/property needed to create a sales order and the relevant configuration and a handful of tips and tricks are carefully explained to counter most practical problems a user might face in course of implementation. While explaining the topics, language is extremely user-friendly and works well for beginners and technical folks who are not well versed in the jargon of SD paradigm.
I believe it was never set out to be written as a textbook but had that been accomplished, this book would have been a more satisfying product. Still, thousands of SAP SD consultants and enthusiasts refer to this book as a textbook and are usually satisfied. Not many books come close.