One reviewer says that over 50% of the book is inaccurate. That statement is incorrect, in my opinion. The true percentage is closer to 4% or 5%, mostly in the screenshots and the references to menu items, especially for panels and views. This is unavoidable because there are slight differences between Drupal 7.0, 7.1, 7.2, 7.4 and 7.7. A few menu items are different between the book and the actual Drupal 7.7, but there is nothing of functional significance, just discrepancies (but those discrepancies pertaining to Views can be confusing).
I am a relative newcomer to Drupal who is semi computer-literate (I have been writing Windows desktop programs using the Delphi language for the past 15 years). This book is the first Drupal book, or any book, that has guided me to a successful no-pain installation of Apache-MySQL-PHP plus Drupal on my Windows system. The reason was that the writer was very specific about things such as folders, using plain language without unnecessary technical sidetracks. (By contrast, there is another book on Drupal 7 that has an unfinished discussion about installing Apache-MySQL-PHP that left me dangling, followed by an equally hasty and vague discussion about installing Drupal.)
After guiding me to a successful installation of XAMPP and Drupal, the book covered the broad sweep of Drupal's functionalities, giving me a basic working knowledge of Drupal without bombarding me with things such as PHP.
In summary, this book is an excellent fast-track to Drupal, one of those rare books which offer much gain with no unnecessary pain. The foundational topics and the more advanced topics in this book are well developed, and will take you well into the intermediate Drupal level.
UPDATE: I have gone through two other Drupal 7 books, but the one by Mercer is the best of the three, in my opinion.