I just published my first Review on Amazon.com (roughly translated from German):

Ideal starting point into the world of modules

I have used Drupal on several websites for years. Only the Development of custom modules, i.e. individual extensions of Drupal, was never really clear to me. All those online tutorials, documentation and API descriptions were too complex and unstructured.

Using "Drupal 6 Module Development", initial problems were much easier to take. The reader gets picked up at a common Drupal knowledge level and is lead towards different topics (construction of modules, theming, hook system, jQuery/AJAX etc.) in appropriate steps. Having read the book one obtains a well structured outline of available online ressources, which additionaly serve the demand of further reading.

This book is a good help for getting started with the development of Drupal modules and wakens the appetite for more.