Ask HN: Book Recommendation for Ajax/Rails?

I've been coding in Ruby on Rails and PHP for a while, and have a very light level of Javascript knowledge. I'd like to learn more about Ajax in general, as well as Javascript Integration with Rails, and I'm looking for some good books. I found this (Ajax on Rails) http://shop.oreilly.com/product/9780596527440.do but I believe that Javascript integration changed considerable with Rails 3 and I'm concerned that this book might be confusing. I'm also looking at Ajax the Definitive Guide http://shop.oreilly.com/product/9780596528386.do but again I'm concerned with the age of the book (2008).

So I'm looking for suggestions. I'd like books similar to these- or do you think that either of these books are an acceptable place to start learning?