lavani is right,
EJB 3 5th Ed by Oreilly is the most recommended book for the said topic. Not surprisingly it is also the most widely used study guide (so far) for SCBCD 5.
EJB 3 in Action on the other has been suggested to be well fit for those who want an easy to read guide on the topic. (some say the tone is similar to head first)
But if you want a free alternative, Mastering EJB should be alright.
[ August 13, 2008: Message edited by: Paul Michael ]