This one is tough. It does a GREAT job of explaining node-isms, but unfortunately I have to deduct an otherwise 5 star rating because of one pretty big problem.... the author writes the book on the new ECMAscript standard, but does so using pretty poor practices for the new features, and the points where the features are introduced, they are done so poorly, or incorrectly.
For example, the author uses the 'let' assignment keyword inside a non-iterative, non-closing function, and then goes on to describe the 'let' keyword as:
"let declares a variable, but a variable declared with let can be assigned a value more than once."
And no other explanation to go with it. For an inexperienced js programmer (likely a high % of the readers of this book), this will lead to problems, since the exact same definition could be used with the 'var' keyword.
I know the author had a difficult decision to use/not use the new features without spending time outside the scope of the book, but I do feel the way the features are used here could lead some beginners into problems down the line.
If you are new to Javascript, read a good beginning js fundamentals book first (Javascript Ninja, You don't know js, Javascript the Good Parts... to name a few), or at least the first few chapters of one of those, before coming to this book to avoid this potential pitfall.
All in all, the best beginner node.js book I've read/reviewed thus far. Looking forward to a 2nd edition!