This book is the first one I read from Packt Publishing and I was surprised by its quality.
It is split in well-defined chapters that allow you to go straight to the point.
In spite of the fact I already knew about some topics covered, I still enjoyed reading those parts thanks to good and clear explanations.
One of the problem I sometimes encoutered is the lack of ponctuation which can be misleading for non native english speakers.
Else, it's a very good book !
More information : http://www.packtpub.com/developer-guide-for-ejb3/book