Drupal is a very powerful content management system that can also serve as an excellent web application development framework. The features provided by Drupal are very comprehensive, flexible, and there is a large community of excited people supporting its development. Pro Drupal Development is a developers tome worthy of the system it documents.
While you can do a lot of flexible and powerful things with Drupal (especially if you install Views and CCK) it offers a rich programmers API and application framework. Pro Drupal Development dives right into the middle of the code and spends very little time at the user interface pointing and clicking. In the second chapter you're shown how to write a module, and in every chapter afterward at least half of it involves coding.
