I like the RESTful Web Services book because it discussed how to design an API and why, not just the functions you'd need to wire an API together.
>don't bother with RESTful Web Services
I agree with you about AWDWR but I'm not so sure about this. RESTful Web Services is very good, and gives a much broader perspective about how & why REST works than you will get from just using Rails 2.
And don't bother with RESTful Web Services.. if you're using Rails 2.x then you only need a half page tutorial on how to use REST, not an entire book.