WordPress All-In-One For Dummies is eight books in one. Each minibook could easily stand alone, but combined, they give you a comprehensive WordPress reference guide.
This book isn't designed to be read from cover to cover, unless you want to! Reading the entire book from start to finish will surely give you an excellent and comprehensive understanding of WordPress. However, there may be aspects of the WordPress software that you are already familiar with and can safely ignore; whereas, you may feel you need to read other sections of the book to get the information you need. Feel free to take what you want and leave the rest!
You can also flip to the comprehensiveindex of this book to find out what information is covered or search for the topics you want to read about.