This book promises to give the beginner a good grounding in XML by following each of its lessons for 60 minutes a day, over 16 days. As always, with this kind of title (learn in 24 hours, 21 days or 7 days), the attraction is the prospect of doing a few lessons and becoming proficient in a minimal time. It's important to remember that you'll still have to do the work, whatever the time schedule and breakdown of lessons. There isn't any way of magically learning without doing any work.
The book is aimed at complete newcomers to XML with no previous knowledge at all. If you've had any previous experience then some of the information in the first few chapters will be redundant. Strangely, straight after the basics the next subjects to be covered are DTDs and XML Schema. I think these are a bit daunting for the beginner and even though a lot of effort has been put in to providing a gentle introduction I felt that these might have been better as later, rather than earlier lessons to avoid the risk of putting people off completely.
XHTML, CSS and XSLT are are all covered and these sections would, generally, be most useful to anyone learning XML for the purposes of developing or maintaining websites. It is assumed that the reader already knows HTML, with the XHTML chapter just giving a description of the differences between HTML and XHTML and a guide on its use, rather than a guide to writing web pages with XHTML. The CSS and XSLT chapters both outline the basics, but anyone wanting to use them for serious work will need further material and would probably be better off with a different, specialised book.
The book does not cover using XML in conjunction with a programming language such as Perl or Java and concentrates on website development rather than application development.
It's a reasonable introduction for the complete beginner, but less useful to anyone who requires more than the basics. The content would need to be supplemented by other books for anyone using XML regularly for software development.