No matter that I already have expertise with JavaScript, I decided to read the book because there're many positive comments about it and filling some gaps in my JS knowledge. In the end, it turned out to be very helpful. I learned a few things and answered some questions of my own, which I found valuable. I would suggest skimming the book, finding the sections where you want to dig deeper, and keeping the book as a reference. At least, that's what I did.