First, the book is aimed at non-developers, the first two chapters of the book cover Joomla’s history and the different ways to install Joomla. Chapters that follow cover setting up users, creating and organizing content and navigation. If you’ve set-up a Drupal site, a lot of this will be quite familiar.
Starting with chapter seven, extensions are covered. Some of these are built-in, but many more are findable at the Joomla website. When it comes to extensions, Joomla breaks them down into three groups: Components, Modules, Plug-ins. Components include things like photo-galleries, banners and others that are like mini-applications, usually with a administrator and public parts. Modules are smaller parts that usually appear on the site in boxes on the layout, examples of modules found on most sites include: the footer, log-in or a block displaying the newest content items. Finally, plug-ins are extensions that react to events (possibly triggered by other components or modules) and can be used for things like filtering out swearing from user comments or adding social-bookmarking buttons to articles. One of the thing this book does well is introduce readers to some of the better known extensions and how to find and evaluate their suitability for a project.
Of course, no CMS would be complete without a theming system. Templates are explained in chapter 10. Readers are shown how to modify templates but not create one from scratch.
After 11 chapters on the workings of Joomla, there are two chapters on putting together a simple personal and business site using some new extentions. The book then wraps-up with three chapters on users management, languages and site administration.
For a reader new to Joomla, this is a good book to explain how to get going understand how the whole system fits together and putting together a simple site.
Book’s website: http://www.informit.com/store/product.aspx?isbn=0321703782
Extensions explained: http://docs.joomla.org/Tutorial:What_Are_Extensions