Rating: 

First of all, it is unnecessarily thick, which makes it more like one of the
'* in 21 days' books; the author repeats himself often.

Second, although the author shows that working with XML really means
reading or generating a tree, something that programmers have been doing
for the last thirty years, he is not willing to admit this directly,
and presents XML as some sort of unseen magic.

Finally, the book is written in a "packer" style, and not a "mapper" style
(were "packer" and "mapper" are as described in "The Programmer's Stone"
available on SlashDot).

Having said that, I have not heard of any other book that describes
practical usage of XML. Therefore, I still advise to read the book,
just to get started.

I wish that all o'rielly books were as good as 'Advanced Perl Programming'.