jQuery in Action
is a fast-paced introduction and guide. It shows you how to traverse HTML documents, handle events, perform animations, and add Ajax to your web pages. The book's unique "lab pages" anchor the explanation of each new concept in a practical example. You'll learn how jQuery interacts with other tools and frameworks and how to build jQuery plugins.
jQuery Fundamentals (http://jqfundamentals.com/) (I read it, and it's useful)
jQuery Succinctly (http://www.syncfusion.com/resources/techportal/ebooks/jquery) (I didn't read it, but the author is reputable, and a good writer)
Moreover, this site has a lot of useful articles: http://www.learningjquery.com/
Well for beginners, i would suggest to try jquery tutorials from w3schools rather than a book because it has easy to understand tutorials along with enough description to understand them.
