I have been working with this particular book now for a couple of months now and I have to say that it is one of my favorites.
Sam’s Teach Yourself PHP, MySQL and Apache. – this link goes to Amazon.
This book is perfect for where I want to go with Drupal. xAMP is the Drupal backbone and this book covers everything that I need from the last three letters of this acronym. There code sample are well documented and helpful. Check it out if you plan to be able to develop for Drupal and not just implement the modules and themes that are on Drupal.org.