Pretty good book. Nicely written in a conversational style, and it moved at a fast, but manageable pace. My only complaint was that it didn't always give complete directions on how to assemble the various parts of the application that is was building. In addition there were parts of the code that weren't described in the book but were required to get the application running. I understand that he didn't want entire listings in the book, but it would have been nice if he had been more explicit about when he was leaving something needed out.
Also, I ran into a version problem using the latest Socket.io package. Never quite got the client-server version of the 5x5 word game to work due to this. May revisit at a later time.