The third edition is still an excellent book for Drupal 6 development, but despite its title it fails miserably at detailing the many changes introduced with Drupal 7.
Probably the biggest shortcoming of "Pro Drupal 7 Development" is the inadequate coverage of Fields API. One major change of Drupal 7 was the integration of CCK (now known as Fields API) into core. While the book explains how to define fields in the UI (which is off-topic for a book on programming) and how to create custom fields, it lacks an explanation of how to work with fields programmatically. Consequently, it remains unclear how to migrate content based on custom node types from Drupal 6 to Drupal 7.
Other major changes of Drupal 7 include Entities, which unify nodes, users, and comments into one common concept, and Render Elements, which radically change the way theming works. Alas, neither Entities nor Render Elements are even mentioned in this book.
It is obvious that "Pro Drupal 7 Development" was rushed to market. The index is sketchy, some flow diagrams of the second edition have been replaced by blurry jpegs, and code examples are formatted sloppily (wrong indentation, poor word-wrapping). Many chapters refer to the Drupal online documentation for "up-to-date information".
For Drupal module developers who already own the second edition and who just want update their knowledge for Drupal 7 the book "Drupal 7 Module Development" by Matt Butcher is a much better choice.