O'Reilly's "Javascript: The Definitive Guide 5th Edition" by David Flanagan teaches Javascript really well including Ajax and DOM.

The first half of the book is a Javascript tutorial while the rest is a language reference. Good book.

And, after reading the Definitive Guide:

http://www.packtpub.com/jquery/book

Didn't we just cover this? Yes, yes we did: http://news.ycombinator.com/item?id=61311

except that the free download link for the pdf mentioned has since been removed.

inurl:javascript.the.definitive.guide filetype:pdf

Best book hands down for learning JS is called Simply Javascript from Sitepoint written by Kevin Yank and Cameron Adams.

Take a look at the videos on Yahoo by Douglas Crockford on the Javascript Programming Language, and his "Advanced Javascript". Very well presented.

http://developer.yahoo.com/yui/theater/