One of the authors, Elliotte Rusty Harold, is no stranger to the technology. He is an early adopter who has written two previous XML books (and several good Java books) and created a web site devoted to XML (Cafe con Leche).
This book is divided into 4 parts. The first covers the essentials of XML including XML syntax, DTD and namespaces. The second covers 'Narrative Centric Documents' involving XSLT, CSS, XLinks, XPointers and XPath. The third covers 'Data Centric XML, ' involving DOM and SAX. The final part is a quick reference to all the above. Each part contains tutorials that are concisely written and packed with practical examples. Beginners can use it to jump-start their learning experience and experts can use this as a indispensable ready reference.
XML Schema is mentioned but not covered in this book.
Hats off to O'Reilly Associates for producing a professionally attractive, well-designed and portable book. It is comfortable to read and to hold. Stranded on a island and allowed only one XML book, this is it!
Page 35: ?, *, + are all listed as allowing zero or one element, where they are actually each unique.
Page 133: The authors show linking in an XSL Stylesheet in an XML Document and they list the type of linked in document as "text/xml" which will NOT produce the desired result. They type should actually be "text/xsl". (this can be a quite frustrating error to debug)
Similar examples are scattered throughout, plus their decision to not even discuss XML Schemas leaves me a bit puzzled, but I knew that when I bought the book so I can complain too much.
If you need a good reference to XML, and you can overlook small errors, then go ahead and purchase the book. If the errors bug you then I suggest you wait for the second edition.
This book scratches the surface of several XML topics like DTDs,XLink,XPointer,DOM,SAX,CSS etc, but doesn't explore any subject in detail. However one glaring omission is XML schema.
If you are a techie trying to learn XML or an experienced professional looking to enhance your understanding of XML and the related technologies, then Professional XML from Wrox press is a much better bet of your money.
Overall the most useful section of this book is the reference section at the end and is well worth the money if what you want is a good reference book.