I have currently examined and read a few books on EJB.
There really aren't that many at all, and not all are up to date
nor that good.

The best book I've read this far is:
"Enterprise JavaBeans" by Richard Monson-Haefel (O'Reilly). (It's listed
on the Related Links in this forum). Make sure you buy the
latest edition which covers EJB 1.1.
It's by far the most comprehensive book, and it is well-written
as well.

Another book which was quite ok but not as comprehensive
is "Enterprise JavaBeans - Developing Component-Based
Distributed Applications" by Tom Valesky (Addison-Wesley).
It does not give you the same deep understanding of EJB
as Monson-Haefel's book but it can get you started writing
some EJB:s.

There is also a free pdf-format version of Ed Roman's
"Mastering Enterprise JavaBeans" (Wiley) available at the
site theserverside.com (http://theserverside.com/resources/book.jsp).
Registration required.

Then you would of course have to read a lot of vendor-specific
documentation covering your choice of EJB Container/Server in
order to see what EJB *really* can do for you.

Regards,

Jonas Bergqvist