Hey there,
Before I did anything with Joomla! I read a book called Joomla! 1.5: A User's Guide: Building a Successful Joomla! Powered Website (2nd Edition) (Paperback)
I found it fairly useful but nothing beats setting up a server on your PC using something like WampServer and then creating a Joomla! test site with the sample data installed.
Then just roll up your sleeves and wade in! There is a built-in help feature which can at least give more detailed info on most aspects of the various components.
And if you have specific questions then I guess try posting them here.
Also - come to the Sydney Joomla! Users group meetings - lots of Joomla! gurus attend and if you twist their arm and push them into a corner, or ply them with alcohol

- they can probably give you valuable insights.