I disagree. To me, it shows that there are many great books that offer a lot to people and while there's overlap, each book offers its own unique value. For example, "JavaScript: The Definitive Guide" is an amazing book but incredibly tough to read, IMO, due to verbosity. But it's a book that has been invaluable to me because of the breadth of coverage of the JS language. I tend to use it more as a reference. I personally find "Professional JavaScript for Web Developers" to be as good and much more readable, especially to people who are just now getting into JavaScript. 

Stoyan's book on OOJS was awesome because it helped me better understand the ins-and-outs of OOJS, something that, due to my love of jQuery, I had tended to overlook. I think a lot of developers could probably relate to that as well.

And yes, I do read a lot but it's not because I have "too much time on my hands" or that I'm lost, but more because as a professional developer, I like to look at new material all the time. If you're not doing that, then you're not doing what you need to stay on top of your game. You need to make the time to continue to learn. Just reading "Professional JavaScript for Web Developers" has been incredibly valuable as I've learned about things that I've either taken for granted or not known about. To me, that's value and makes the book essential.

And lastly, yes, I'm part of the jQuery project team so I need to stay on top of these topics so I can contribute to the project and the community in the best way possible.