The book is full of code samples that borrow heavily from YUI both in concept and source code, though I wish the attribution was a little more transparent in some places. Still, it shows just how design-pattern centric YUI and other libraries are, which is an important point to make.
This book also suffers from a common problem among design pattern books: sometimes two patterns are so similar that it’s hard to determine when to use one over the other. Is it a facade or an adapter? The line is incredibly thin between the two. I would have liked to have seen a final summation chapter that listed each pattern including indications, contraindications, and related patterns. Ross and Dustin do make some attempts at comparing certain patterns in the book, I just would have liked to see such comparisons called out more strongly.
Disclaimer: Any viewpoints and opinions expressed in this article are those of Nicholas C. Zakas and do not, in any way, reflect those of my employer, my colleagues, Wrox Publishing, O'Reilly Publishing, or anyone else. I speak only for myself, not for them.