Having just completed reading/practicing java servlet programming (also by o reilly) I was pleased to find that this book was also as accessible and as concisely written.
It demonstrates and explains the fundementals of EJB and helps the reader keep up with the latest developments (ejb 2.0), - for example container managed persistance is not backwards compatible with 1.1.
All the major areas are covered, and the accompanying examples are excellent. -Highly recommended.
The first three chapters are essentially background material. However being relatively new to this area of java programming, they set the scene by describing the underlying technology, architecture and ejb runtime management.
Chapters 4 - 8 covers Developing enterprise beans, the Client View, Basic Persistence, relationships, and ejb ql.
Chapter 9 refers to EJB 1.1 spec, which probably is not relevant for new projects.
Chapters 10 -13 covers Bean-Managed Persistence, Bean-Managed Persistence, The Entity-Container Contract, Session Beans and Message-Driven Beans. Again, the examples are excellent.
Chapter 14, transactions, is one of the longer chapters that explains how they work in EJB. Although complicated , its clearly explained.
Chapter 15 is a priceless Design Strategies chapter that I expect would be useful even to experienced EJB developers.
The last 2 chapters, 16 and 17 cover xml Deployment Descriptors and J2EE. The former is an excellent reference and well organized, which aids understanding. The J2EE chapter is short, but gives a good overview how ejbs, servlets and jsp fit together.