O'Reilly Enterprise Javabeans 3.0, and EJB
3 In Action are the most popular titles. Personally, I used Enterprise Javabeans 3.0. But the most useful resource after either of those books, is Mikalai Zaikin's notes. I used those after reading through the EJB 3.0 book without taking any notes, and passed the exam no problem, everything had been referenced somewhere in the notes. Good luck!