Recently, I pulled out my (mostly) unread copy of Perl and XML and rather than using it as a reference, began reading the entire thing starting with the Preface. It was a very enjoyable read. The fact that I enjoyed reading it so much was a surprise to me - who would've thought it possible? I had worked with XML and RSS and LDIFs for a dozen years. In the past, I basically just did a quick google and then thought "Yeah, there's the module I need" and installed it an ran with it.
This book explained the differences in the many modules and explained when and where to use them. After nearly eight years I had an "Ah-hah! That's why that program sometimes didn't always catch everything I was looking for!" (I was using a generic XML parsing module when I should've been using XML::DOM.
My only criticism (a minor one) is I would have liked to have seen more and varied examples in the RSS chapter. But, it was an XML book, not a RSS book and the goal was not to show you the difference between Atom and iTunes in RSS feeds, etc.
If you use XML and Perl - you will want to READ this book. Note: I said READ this book. Don't just buy it as a reference and put it on your shelf like I did (at first). In fact, everyone reading this should buy it! (It's only one penny on the used market at Amazon.com. Why not?!)