Its very easy to learn EJB 3.0 if you know EJB2.x (for basic remoting concepts, middleware services etc.). I think if you are not familier with EJB2.x, you can start easily. There will not much dependecy.
Yes. i also agree that, "EJB3 In Action" is great. Inface, all the "In Action" series books are good. We are also using EJB3 in our application. You can follow these online resources for quick learning.