1. Designing Enterprise Applications with the Java 2 Platform, Enterprise
Edition by Nicholas Kassem & co, Addison Wesley
2. Mastering Enterprise Javabeans by Ed Roman, Wiley Publishing Co - A must
read, J2EE bible for for any J2EE developer.
3. EJB Design Patterns by Floyd Marinescu, Wiley Publishing Co - Very essential
EJB patterns.
4. Java Enterprise Patterns by Mak Grand, Wiley Publishing Co - Lot more
useful patterns.