I think i should not introduce you with the Joomla. I believe most of the net surfer more specifically who have website and/or want to build website have already heard about Joomla. “Joomla” is enough for addressing Joomla.
Though Joomla is very user friendly, people having little or no experience with PHP & Advance web development may be in stuck with the arrangement of Joomla. I even have to expense a lot of time to understand it because I never like to go through the thousands of pages online documentation. Unfortunately, that time there was no concise manual/book on Joomla.
But I thank Packt Publication for publishing the book titled “Building Websites with Joomla! 1.5 Beta 1” written by Hagen Graf. This book nicely outlined the basic understandings of Joomla. Yet some readers having ideas with Joomla may complain about the book. I have read some review where the reviewer claimed all the things of this book is already been covered in official joomla manual. But still I recommending the book for people who have no idea with Joomla. Because who have times to read so many pages of manuals. Joomla is easy thing. So get a introduction and you can play with it.
Not only customizing Joomla to suit your site, this book shown how to create your own template and extenstions. Tough very basic, buts its a good starting point to develop you own extenstions.
So, if you are new to Joomla and want a good starting guideline you may have this book. For a beginner it will worth at least 80% of your money.
For about it: http://www.packtpub.com/joomla/book