If you are particular about JBOSS use this book
Enterprise JavaBeans, 3.0
By Bill Burke, Richard Monson-Haefel
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Publisher: O'Reilly
This book is good enough with lots of practical code. They also demonstrate building ejb etc through
ANT on jboss .
But before that reading EJB3 In Action (byDebu panda,Reza) sets the solid background for EJB3.0 .
SCJP(1.4), SCWCD, Oracle 9i SQL certified, Oracle PLSQL Developer Certified Associate