Some PROs and CONs...
Pros:
Topic flows very well. Author was able to explain each topic without asking reader to refer to upcoming forward chapters. Best part of this book are the examples. They are relevant and short and sweet enough to understand. Best of all, there are lots of examples. The author doesn't just slap them on the page and tell you to figure it out yourself. The author walks the reader thru them.
Cons:
Some areas reads like a technical manual.. causing me to reread sentences over and again. But that said, the book still comes across as tutorial friendly (You figure that out.).
Comparisons:
I rate the book 5 stars. I own Beginnning XSLT 2.0 by Tennison, XSLT 2.0 by Kay, and Mastering XSLT by White. My opinion is that XSLT in 21 days is the best book to get you to learn it the quickest because of the author's superb examples.