I had a need to add a tiny amount of JavaScript to a website, and it became evident that using jQuery would be the right approach -- it makes using JavaScript so much easier! But, while I had some knowledge of JavaScript, I was rather rusty, and I did not know jQuery much. So, I looked in my library of computing books, and found this one, which I had not yet read. Reading it was far more of a background than I needed for this task, but I decided that it was time I learned a little more about JavaScript, and especially jQuery.
This book is an interesting amalgam of elementary topics and more advanced topics. I found the elementary topics to be a good refresher, and the more advanced topics very useful. I have years of experience as a software engineer, and so I had no difficulty with any of the topics. I didn't follow along with the hands-on exercises because my goal was rather short term; if I were advising others, I'd strongly recommend doing those hands-on step-by-step exercises, because I'm a believer in learning by doing.
I'm not sure whether a beginner would get overwhelmed after a while going through this book. But I think it is a very good start; perhaps a beginner would learn in chunks, getting comfortable at each stage by playing with JavaScript and jQuery, and then returning to continue through the book.
I think this is a very good book, and don't know of many others that do as good a job. In particular, this book concentrates on jQuery quickly, and avoids the many arid side roads in JavaScript. In many ways, jQuery does a lot to fix the many problems of JavaScript, not the least of which is a lot of complex areas that are not particularly necessary to learn in order to proceed. There are many JavaScript books that tend towards the encyclopedic and lots of reference material, but they tend to obscure those areas which are most useful to learn.