By the same author of last year’s well-regarded front end drupal; This similarly-sized book is aimed more at beginners.
If last year’s professional WordPress is the must-have book for WordPress developers, then definitive is at least the equivalent for Drupal developers.
Learn How to Use the Content Management Framework to Create Powerful Customized Websites.
Quickly Building Web Sites With CCK, Views, and Panels
One question that is going to come up is how current is this book with the recent arrival of Drupal 7? Except for CCK, most of the content is still relevant.
If You Have 24 Hours to Spare, Why Not Learn Drupal?
Designing, Theming, Scripting
Tools and Techniques for Learning to Create Themes for the Drupal 6 CMS.
Learning the Many Ways to Theme With Drupal 6