If I have a look at the jQuery website and have a look at the online documentation, it's really impressive: nice explanation, lots of example code, possibility to add comments,... It reminds me to the PHP-documentation you'll can find online (and which I use when I'm looking for a feature/function). (I wish the RCP framework was documented like this).
Does the book has any added value besides this valuable information?
Some related questions: If a new (major) version of jQuery is released, will the book keeps its value? And how long will it take to release a book dedicated to this new version (jQuery is a fast evolving technology and a book will always be based on an "older" version)?
I absolutely think the book adds value! jQuery (and other libraries) brings about a complete paradigm shift in the way Java Script is used. The basic explanation of Jquery selectors is invaluable and so is the information on writing jQuery plugins.
I doubt if the fundamentals would change in newer versions. The jQuery documentation does a good job of documenting the in-build functions. The book on the other hand points out how its structured and helps understand it better.
I first started using jQuery because I read the book (yes that was a few years back!), so maybe its a biased opinion
The online docs for jQuery are among the best. But online docs are great fro reference, but don't always do a good job at teaching how things are best used, and how to use methods in conjunction to get real-world tasks done.
The book stresses modern jQuery best practices and the examples are geared to go beyond what's possible in online documentation.
Because jQuery is becoming more and more popular, it seems to become the standard JS library (if it hasn't already reached this status ) So as a jQuery newbie (mainly because last 2-3 years I wasn't doing a lot of web application development, nor using JS a lot) it will be very interesting to acquire (or with a bit of luck win) a copy of this book to learn the best practices about it and use the API as a reference for quick lookup.
I remember re-engineering my brother's futsal team website with PHP (original version was just html, js and xml files containing the data without using a js library, that was fun developing and debugging ) as a php-newbie too, it was hard to find best practices to develop this website and I had to refactor it several times.
But I wouldn't underestimate the value of (the online documentation together with) the user comments, because you get snippets, enhancements, remarks,... from novice users but also from real experts (and they were really helpful). Of course you sometimes have to look through 50-60 comments, so it's not as nice presented as in a to-the-point (and according to the reviews, great) book and thus it can get very time consuming.