I think the best learning path towards the SCBCD 5.0 certification (IF you don't want to read directly the specification) is:
1- Enterprise JavaBeans 3.0 - O'Reilly. 2- Pro EJB 3 Java Persistence API - Apress. (Chapters 3 to 7) 3- Mikalai Zaikin Notes (With the Specification in the other hand since MZ maps every certification objective to the specification's specific chapters).
It takes around 3-5 months with 2-3 hours of daily work.
This chapters expose a really clear and concise vision of EJB 3: Persistence API and Transactions. It talks about the Core too but for that subject I found O'Reilly's book just as good, but for Persistence and Transactions this is an excellent book.
I think it would be perfect to propose this reading in the study group (In fact, some people that already passed the exam strongly suggest this reading here in the javaranch forum).
It is about 150 pages, so it is not such a long reading comparing with the other books and Specs.