As as a veteran of 12 years experience in Software Engineering field, and who wanted a speedy primer on Drupal, this ebook certainly got me started.
This ebook outlines the bigger picture, from which you can dig deep, and all the resources are mentioned in it.
After reading through this beginner guide, you will know what to look for further, as it introduces you to the taxonomy required.
To quote from the guide:
"This very basic guide is intended to give beggining Drupal developers information to help them get started with the platform. It is barely possible to provide all the information necessary to excel at Drupal in just a few pages so I recommend that you dedicate some time each week to searching out new resources and tips on how to improve your knowledge of the platform."
As of July 2012, this guide is uptodate, and because of it's generic nature, should be good for a long time for a person who is starting to learn Drupal, but in any case, if you notice something that is outdated, please contact us.
Another beginner guide for PHP: Introduction to PHP in pdf
To download the full ebook, right click and choose "Save Link As", then download more free ebooks.