The more book reviews, the better:

Looking across the XML bookshelf today, it's easy to see many books discussing XML in a generic manner, or more commonly how to utilize XML within Java, .NET and Perl. Moreover, despite the broad based support that PHP has for XML, there has been no book that tackled the complexities and best practices, and at the same time offered a comprehensive resource to the XML-based APIs -- at least not until now. Read on for more about the best selling Professional PHP4 XML.

Slashdot.org has this review of the Wrox book PHP4 XML released a little while back. According to the reviewer, it's one of the best PHP/XML resources out there to date, giving it a nine out of ten in the ratings. One thing that makes this book stand out from the rest is that they don't just give the code and explain it like most - they take the examples and show how they could apply to common problems that programmers face every day. They even have a link to a sample chapter that you can take a look through to see if the book is right for you.