Drupal 5, Drupal 6, Drupal 7, and, now, Drupal 8 are all powerful platforms for cultivating, developing, and managing the ultimate User Experience. Support for Drupal 5 and 6 might have ended, but resources for each are still available if emerging Developers wish to dig into the 'History' of Drupal.
Other platforms such as Wordpress, Joomla, DotNetNuke, Ethereum, Ruby on Rails, and beyond all offer their unique approach to deployed User Experience platforms.
Here-to known as d.o, the Drupal.org Documentation is extensive, detailed, and (at times) as organized as a Frat Boy's bedroom. The Drupal Cookbook for beginners, for example, looks like a project put together by dozens of Remote Developers without collaboration, Version Control, or oversight.
Of course, none of that is true.
Perception, as they say...
With the creeping Normalization across code libraries, platforms, and languages, it will not be long until web-development platforms like Drupal are equally as viable for cross-platform and gaming development as such as the Unity Game Engine or the Unreal Engine (Hint: It is getting there now... Play some SNES Mario: Super Mario World The creator made it entirely in HTML5, CSS3, and Javascript.)
When combined with Big Data engines such as IBM's Watson, Splunk, Loggy & Hadoop, the data normalization becomes even more of a non-issue. These additional tools (which we will not touch in this book) take machine data from any/all sources, harmonizes it then reproduces it in a normalized manner. Just as systems like Unity do for code.
d.o's Documentation pages need to rise to the occasion as well. Perhaps, in the future, this book may help with that.