Hi
Head First book are one of the best options, right now they are having Head First EJB, but its for the previous version, i read some interesting post in their site hinting that they are working on the new version and going to be released probably this year, also they were looking for an author for a while.
In the mean time i'm using EJB 3 In Action from manning, so far so good.
Good luck there.
Sergio