Joomla! : a user’s guide : building a successful Joomla! powered Website / Barrie M. North. Prentice Hall, 2008
Joomla is CMS (Content Management System) . A CMS is used to build and organize a web site. It stores all content in a database, and presents it in web pages that have a consistent format (cf WordPress, which this site uses). It can be used to power a blog, forum, or eCommerce site. Joomla was previously called Mambo.
This book is for the web designer, and assumes no knowledge of PHP or CSS. It is an easily read book, and will teach you how to use all the features of Joomla.