I never understood why certain books who are covering a framework or a very particular aspect of programming must start with what is basically a short tutorial about the programming language they are using. Maybe it's just me but I always assumed that someone who buys a book about JQuery already knows Javascript and if he doesn't a short tutorial just isn't enough. Take a look for example at [Hacking - The Art of Exploitation](<a href="http://nostarch.com/hacking2.htm" rel="nofollow">http://nostarch.com/hacking2.htm</a>), a great book that deals with stuff like buffer overflows, network sniffing and shell code injection but starts with a tutorial about C...
I've never touched JQuery. I learned Javascript, and by the time I was comfortable enough with that I didn't really want to have to be bothered with an unfamiliar syntax. If I've ever needed to accomplish something repetitively, I've written my own little (and probably very badly-optimised) JS library - that's definitely helped me understand more about JS than using JQuery ever would.
I love this book! The advanced topics really helped me out with some performance issues I was having with my own sites.<p>Definitely a recommended read.