If you don't care for technical books that read like text-books, reference manuals or legal documents, this book is the EJB 3 book for you. I really like the humorous, readable and down-to-earth feel of the O'Reilly Head First series books (sadly there is no Head First EJB 3 book yet). This is no Head First series book, but it is a good substitute.
The book explains the basic concepts very well, provides practical code examples and focuses on the most useful EJB 3 features. This book is ideal for Java server-side beginners, but there is ample material to keep a salty old sea dog engaged. The difference between this book and some of the older, more reference-oriented EJB 2 books is striking (as is the difference in EJB 3 itself). I was really impressed with the coverage of Spring in the book. It�s good to see books that don�t pretend as though competing technologies do not exist.
Besides the contents of the book itself, I found the downloadable GlassFish example code invaluable in getting started with EJB 3 applications. The author forum for EJB 3 in Action was great too. It was fantastic being able to talk with the authors on a one-to-one basis.