Software developers of Web-based applications looking for a way to modify their user interfaces more quickly and easily without worrying about platform dependencies will probably find this book well worth their time and money. XUL, which stands for “extensible user interface language,” is pronounced “zool,” a tongue-in-cheek pun from the 1980s Ghostbusters movie. XUL leverages Extensible Markup Language (XML), cascading style sheets (CSS), Hypertext Markup Language (HTML), extensible bindings language (XBL), JavaScript, and the resource description framework (RDF) to make designing and developing platform-independent user interfaces an easier task.

According to the introduction, this book is intended for software developers, and with one exception, it remains true to its intended audience. This book is a little too technical for Web developers who know only HTML, or who create Web pages using only Web development software like FrontPage. The book should be useful to both novice developers familiar with Web-related technologies and markup languages, and to experienced software engineers, though more experienced developers may choose to skip a few of the early chapters.

Chapters 1 through 3 provide introductions to XUL, XML, and CSS. Chapters 2 and 3 cover only the fundamentals of XML and CSS, and can be skipped by those who already have a working knowledge of these technologies. If their objective is to become experts in either XML or CSS, readers should find another book. These chapters, however, provide enough of an introduction to XML and CSS to get started with XUL.

Chapters 4 through 7 delve into more detail about building XUL interfaces and creating themes, templates, and overlays. This section of the book not only details procedures for how to accomplish these tasks, but also explains why these tasks are important.

Chapters 8 through 10 explore the open-source project for a Java-based XUL (jXUL) rendering engine. In addition, they detail two case studies to provide in-depth, real-world examples of using XUL to build enterprise information portals on the Web, as well as interfaces for an e-commerce Web site.

The appendices serve as an excellent standalone reference source, detailing all XUL elements and their associated attributes, document model object (DOM) methods, JavaScript functions, and event handlers, as well as providing a cross-reference to Netscape theme components and cascading style sheets.

I found only a few flaws with the book, most of them minor. In chapter 2, “An XML Primer,” the book asks the reader, “What is a markup language?” and then proceeds to explain. The introduction, however, states that “this book assumes a basic knowledge of Web technologies and markup languages,” so the first few pages of chapter 2 miss the intended audience completely, and should not have been included in this book. If you’re learning something new from the beginning of chapter 2, it’s unlikely that you will understand t he rest of the book.

The editing is a bit sloppy, but the errors seem to be inconsequential. The text refers primarily to “a XUL,” but sometimes uses the phrase “an XUL,” which I found distracting. Also, XUL is defined as both “extensible user interface language” and “extensible interface language.” The body of the book defines CSS as “cascading style sheets,” but the index defines it as “cascaded style sheets."

The index is sufficient, and contains adequate entries, but it doesn’t define its typographical conventions, for example what boldfaced page numbers or page numbers followed by an italicized “t” mean. A short glossary might also have been helpful. The index lists the acronyms in their spelled-out forms, so readers have to know what the acronym stands for in order to find it. A list of figures, tables, and sample code would have also been helpful near the table of contents. In addition, a ring binding may have been a better choice for the book’s form, as it kept closing while I was trying to type some of the sample code.

Editing mistakes notwithstanding, the book is well written and has an easy-to-understand, conversational tone. All chapters contain summaries, which is particularly helpful in some of the later chapters, where the concepts are more complex. The book’s figures are clean and easy to understand. And perhaps most useful, the book contains plenty of sample code to get new XUL coders started. Once readers have become familiar with XUL, the book should continue to be useful as a valuable reference.