I like Marchal's style - friendly and informative, however he badly needs an editor to knock this book into shape. The chapter on DTDs would confuse Einstein even though DTD is one of the easiest concepts in XML. The chapter on namespaces is good but overly long. Stylesheets are explored in a good level of detail with a very nice walkthrough example - up to a point - then he introduces some advanced stylesheet topics with almost no explanation of them.
Very good advice to the beginner on where to download xml tools and good references to the W3C recommendations, etc.
Great chapter on the DOM and SAX APIs and the example e-commerce application ties a lot of the concepts togther.
My gripe all the way through the book is that he starts with a very good explanation of a topic, then when you are starting to feel comfortable, he will introduce new information with almost no explanation or a bad explanation. Perhaps this is the sign of someone who understands the topic too well and cannot relate to the poor old beginner.
I would still recommend this book - it's cheap enough - but don't feel downhearted if you can't follow all of it. You'll probably have to read it in conjunction with another book - but that's what I ALWAYS end up doing with any computing topic.
I would look forward to a rewritten and re-edited version of this book.