There is something about all things XML that I find makes the subject a tricky one to break into. The difficulty is, I suspect, more due to the complexity of terminology than the general complexity of the subject area. Despite this, I found this book approachable and more importantly, useful.
The text progresses logically from introducing the reader to the basic concepts to the deeper and darker areas of XML Schema. The author is not afraid of showing different approaches where appropriate and discussing the benefits and drawbacks of each. There are also frequent interesting insights into the background of Schema, the ways in which it differs from the less expressive DTDs and the problems inherent with the current Schema language. The final quarter of the book is basically a reference, so it is valuable both to learn from and as a manual.
The style of this book is exactly that which I like to see and enjoy reading. The writing is brisk and concise yet maintains clarity, which helps to keep the book approachable. The style is well supported by a structure based around short chapters; each of which is digestible in a reasonably short time period.
Although I personally find the subject area awkward and non-intuitive, if you need to work with XML Schema, I recommend this book as a very useful guide and reference.