My favorite part of my career is training people how to use Drupal. I've been recommending this book since the day it came out and I got my 1st copy.
I really love how this book starts at the beginning. If you're more advanced you can skim the beginning BUT many people will read and reread the beginning. I'm so glad that it's there.
This book assumes nothing. It lets you know what you need to know. It walks you through the important concepts you need to understand THEN walks you through the steps by step instructions to accomplish the tasks you need to perform as a Drupal site builder and administrator.
The fact that the book is good for Druapl6 and Drupal7 audiences is a pure bonus!
I love Drupal because its awesome. It is certainly comforting to know that this is another awesome book about Drupal!