Programming Firefox, by Kenneth Feldt, a new Firefox book was released a few weeks ago. As the title suggests it is oriented to programmers who want to learn or better understand the Mozilla framework. From the Editorial review:

Topics in Programming Firefox include:

• An overview of Firefox technology
• An introduction to the graphical elements that compose a XUL application
• Firefox development tools and the process used to design and build applications
• Managing an application with multiple content areas
• Introduction to Resource Description Files, and how the Firefox interface renders RDF
• Manipulating XHTML with JavaScript
• Displaying documents using the Scalable Vector Graphics standard and HTML Canvas
• The XML Binding Language and interface overlays to extend Firefox
• Implementing the next-generation forms interface through XForms

Programming Firefox is available for $37.79 at Amazon with free shipping to the United States.

For more books on Firefox, Thunderbird and Mozilla in general check the Mozilla Links Bookshelf, an Amazon Affiliate.