Definitely a good, simple, clear introduction to J2EE design patterns, this book has the advantage of presenting example code in the form of little applications instead of just snippets and lacks all the 'mystical yadda yadda" that pattern books often employ to make their simple content pass for rocket science. I have been somewhat disappointed by the security chapter which is basically just an overview of the J2EE standard security model. Also, being a book "practice oriented" I would have loved to see details on the deployment of the source code presented. Overall a 3 and 1/2 star book that gets a little bonus for being simple and practical.
Previous knowledge of design patterns in general would certainly help you to get the most from this text. For a simple,clear, no bs introduction I recommend Design Patterns Explained: A New Perspective on Object-Oriented Design
by Alan Shalloway, James R. Trott.