This is the greatest computer book I have ever read.
The first three chapters of the book are an introduction to Java security, and they are very helpful to people who are new to Java security, just like me. The same concepts are covered later in the book in greater detail, so it may appear that there are some repetitions, but in reality the author informs you many times that if you are an expert, you should probably go directly to Chapter 4, and read the advanced topics.
In fact, this is an advanced book. Nevertheless, you will not get lost even if you are a beginner. The author covers advanced topics with a very simple approach and even tells you how to perform the simplest operations. While this can be sometimes boring if you already know Java programming, I guess that basic information is always useful, especially if readers are not very familiar with the topic.
In this book you will find the architecture of Java security as well as advanced topics such as cryptography, SSL, Java and firewalls, Netscape and IE Java security, Java plug-in, and many other things. There are many examples and screen captures that help a lot. The final result is that, after reading this book, you will feel like a Java security expert.
There are some imperfections, but overall, this is a great book. If you are interested in Java security, buy this book. You satisfaction is guaranteed.