EJB 3 in Action was really enjoyable to read. This is a well-structured book and covers just what is really required for Java 5 EE application development. In my opinion it is not the best suited for a beginner: it is easier to understand the text if one already has some experience with EJB 2.0. The book provides practical code examples, best practices, design patterns, and performance tuning tips.
I would strongly recommend this book to anyone who would like to get familiar with EJB 3.0.
P.S. The relevance to the JEE development is out of the scope here :) Personally, I would rather go Spring/Hibernate than JSR220 and JSR291 rather than JSR277.
P.S.2 Why not to assume that Hibernate and Spring are the de jure standards for JEE middleware development, instead of creating EJB 3.0? Political reasons? I think that Sun is still reinventing the wheel with its own "standards" and not making use of the community process.