He writes a MooTools cookbook, but doesn't use the MooTools code style. He uses the XHTML doctype, instead of a HTML5 doctype. He uses document.write. He doesn't even use ' or " consistently. His whitespace usage/indentation isn't consistent. He creates global variables out the <random word>. He has broken examples (var oldies = ...; obamas_oldies.each(...);}. He randomly sometimes decides to save references to found elements, in other places doesn't. He uses an Element's onclick attribute, rather than the addEvent function to add handlers. He uses setTimeout(fn), rather than the moo-style fn.delay().
And that's from just scanning the excerpt posted on packtpub.com, as an excerpt like that is meant to enthuse people about the book, I presume it's one of the better parts of the book. A cookbook is supposed to be a bunch of recipes, easy to use, good to use, for people to learn from. Judging the excerpt, this book is giving bad examples regardless of the reader's level, from style to content to quality, I don't think it's anywhere close to MooTools standards. After taking a quick look at the author's website, and looking at his MooTools examples there, I am rather convinced that his knowledge of MooTools and javascript is quite limited, and that the rest of the book can't be very different from the excerpt on packtpub.com.
