This is the second edition of an apparently highly acclaimed book. It will certainly suit a particular target audience - so ask yourself what you want or need to know about XML and how you want that information presented. You will then know if this book is for you or not.
The book describes XML and its related technologies from the ground up. Its contents include XML structure and use and such excitingly named technologies as CCS, XSLT, DTDs, XLink, XPointer, XPath and XSL. The section on XML authoring software seems a silly inclusion since it will rapidly date the book and it doesn't provide much valuable content anyway - more of a space filler.
The presentation style is very verbose. Whilst certainly readable, the author takes great care to try to explain everything in non-technical language and describe every detail slowly and carefully. Some readers will find this excellent, others will rapidly become frustrated at trying to skim the key technical points from the waffle.
Throughout the book the author presents a 'real world' application in XML (a B movie catalogue). This provides continuity and is a reasonable grounding for the book, certainly an advantage over a purist's XML reference tome. The book is clearly aimed at the 'non-guru'.
In conclusion, a reasonable book if you want a slow paced stroll into XML territory, starting from first principles.