Drupal Books

Book: 

Drupal 5 Themes: Create a new theme for your Drupal website with a clean layout and powerful CSS styling

Drupal 5 Themes, a 250 page paperback, gives people one thing they really want: a guide to creating a custom look for your site using css, some PHP code, images, and a little bit of effort.

It provides a bit of a review of existing themes and how to configure them for a custom look without any new code but also goes into how to create a completely custom theme.

Based on Packt Publiching's history we can only assume that it will be updated for future versions especially since theming has changed for Drupal6.