This book describes various tips of increasing performance of Drupal Version 6. Many tips may be found in the Drupal.org, but focusing the theme of performance and summarized briefly. It's convenient.
Drupal 6 Performance Tips
Drupal 6 Performance Tips: Learn How to Maximize and Optimize Your Drupal Framework Using Drupal 6 Best Practice Performance Solutions and Tools
Author: T. J. Holowaychuk, Trevor James
Publisher: Packt Publishing (2010)
Binding: ペーパーバック, 240 pages