As many of you already know, I have been working on jQuery in Action, a book on jQuery for Manning Publishers.
Almost the entire book is available on MEAP (Manning Early Access Program), and it's going to be published in December of this year.
The book itself is pretty awesome. It tries to give you the information you need with a useful narrative, including motivation for certain parts of jQuery. One of the greatest things about the book, in my humble opinion, are the labs, which allow you to test out parts of jQuery without having to throw together an entire test case. For instance, there's a selector lab, which lets you see, visually, which elements will be selected by a given jQuery selector, and a drag/drop lab, which lets you test drag options via radio buttons and then see the results in action quickly.
It's currently the only book out that covers jQuery 1.2, as well as the important parts of jQuery UI (including stuff like the undocumented callback object that you get in the draggable/droppable primitives). Toward the end of the book, you get full-chapter examples (my favorite is the Ajax chapter, which covers building an Ajaxified store selling boots ;) ), and focuses heavily on jQuery best practices and Unobtrusive Scripting.
The book itself is very much in the spirit of jQuery: short and to the point, while covering the important background material necessary to fully understand the topics at hand (especially non-trivial topics like event binding and Ajax).
Without further ado, you can purchase the book (you'll get the prerelease stuff now and the complete book when it's released in December) at Manning's Site. If you use the coupon code JQM30 before the end of October, you will also receive a 30% discount.