There are basically five types of computer books that can be bought on a given topic:
Pocket guide— contains the bare essentials of the topic (like a 'cheat-sheet'). The audience is a reader who is very familiar with the topic.
Reference manual —contains a summary of the most-used features. The audience is a reader who is already knowledgeable about the topic.
Learning guide—(User's Guide, Developer's Guide, Administrator's Guide) contains a narrative approach for learning the topic, in its entirety, from start to finish. The audience is a reader who is new to the topic.
Encyclopedia—contains every aspect of the topic. The audience is typically a software developer, graphics designer, or someone who needs to use the subject technology at the expert-level.
Quick-start guide—contains a targeted subset of the topic. The audience is a novice wanting to jump-in with their sleeves rolled up.
This book is a quick-start guide. In the world of Content Management Systems, the administrators run the site and keep it on-line, the Content Editors create, edit, and publish content, and the Users view the content. This book best-serves the Content Editor. It's not an exhaustive blow-by-blow account of every aspect of Drupal like an 'encyclopedia' would be, but instead, it's a small selection of information and activities aimed at imparting knowledge in an efficient and interactive manner.