I have to agree with other reviews, this is an excellent book to start learning jQuery. Not that there aren't other excellent jQuery books, but the best ones out there are getting a little dated. If you are just starting, not only is this book easy to read and understand, with lots of great examples, but it's also up to date with jQuery version 1.4.
It seems that this book is selling fast, as of this writing it says 1 to 4 months shipping time! Also, I'm not sure why Sitepoint books tend to have such a small discount on Amazon. Sitepoint likes to get people to buy books direct from them. Not sure why. It seems to be available faster on their web site. I have an eBook version. As of this writing, they are running a 5-for-1 eBook promotion on the Sitepoint web site. But, I got mine through my subscription to Safari Books Online, which I highly recommend.
If you are just starting, or even just want a reference for the jQuery basics, this book is the one to have.