The book incorporates a lot of discussions about XPath but they really get in the way of XPath, beeing presented the way they are. It would have been more effective if the book explained XPath just by including the 30 pages of XPath specification, and instead focused not on explaing, but on discussing aspects.

My main point is that you learn to use, as well as master, XPath an order of magnitude faster by reading the specification than by reading this book.

easy to understand, written with humour reference manual
John E. Simpson has done a remarkable job in elucidating yet another XML-related techology in fun and easy small book. Care is taken to provide comprehensive examples (sometimes with hacker-type tougue-in-cheek approach) which illustrates the points of syntax. One does not need to read the book in comprehensive fashion, after a few chapters, you one can just start coding and refer to the rest as a reference manual.

One thing, however is missing, the book does you why you should use XPath or XPointer. What are the real world examples and applications? And what about XQuery? How is XPath related to XSLT? Those points are left for the reader to ponder about, and this is the only reason I am not giving the book 5 starts.

Falls short in comparison with XSLT related books
From the back page of this book: "XPath and XPointer focuses directly on a critical topic that has been covered only briefly in other books". That is true as far as it goes for XPointer;however there are quite a number of XSLT books that explain XPath. That makes sense, because XPath is mainly used in the context of XSLT. (The other context is XPointer, but that is not official W3C recommendation yet, and will be much more limited in use.) That means that a book that deals almost exclusively with XPath should give a better and fuller treatment of XPath than most of the XSLT related books in order to have added value.

Quite frankly, I do not think that this book fulfills that promise. Chapter 2 "XPath Basics" fails to explain the theory behind XPath in a comprehensive manner, and is a tough read. What I am missing here is a clear explanation of how XPath relates to the DOM Model and XSLT processing model. Chapter 3 and 4 give a pretty decent explanation of how XPath expressions and functions work. The description is not complete however, I missed for instance an explanation of the key() function and element-available() function. What I also miss are the production rules of XPath. A more formal approach, with assistance of the official W3C recommendation, would have given a much completer explanation of XPath. Why was't the official W3C recommendation included via an appendix? Chapter 5 "XML in Action" is solely dedicated to examples. Very useful and clear. Chapter 6 "XPath 2.0" talks about how future XPath specifications are developing. Which is interesting of course, but by it's very nature speculative.

Chapter 7 thru 9 try to explain XPointer. These chapters fail completely for a number of reasons:
a) XPointer is not an official recommendation yet, so the authors are shooting at a moving target
b) XPointer will mainly be used together with XLink, which is not explained in this book
c) I found the explanation incomprehensible.

My advice would be to skip this book and buy a good XSLT book that also covers XPath instead, such as the XSLT Programmer's Reference from Michael Kay.

Focused and to the point
XPath is a crucial but often neglected technology for any developer that need to deal with XSLT in a serious way and it's also fully integrated in many XML parsers, like the ones from Microsoft or ColdFusion. This is a small and very focused book that manages to offer a detailed coverage of XPath mixed with some excellent practical advices. Personally I am not interested in XPointer right now, so I totally skipped the second part of the book, but I think the 120 pages dedicated to XPath are well worth the money