Decompiling Java: Learn how decompilation works in order to properly protect your intellectual property by Godfrey Nolan
If you are interested in decompiling, you should get this book. It is a very interesting read and very informative. In the very last paragraph of the book Godfrey writes:
I've tried my best to make this book easy to read. I've consciously decided to make it more practical than theoretical while still trying to avoid making it just an introduction to decompilers by including and analyzing a working decompiler.
In response to that last paragraph, I would say he did a great job of keeping the book's content on that middle ground of not introductory material and also not a deep theoretical analysis, but still very informative. He also does a great job of covering some of the “Tools of the Trade”, even making sure that both sides of the cat and mouse game (decompiling vs. protecting against decompiling) are covered. As someone who is trying to design a .Net decompiler, I found the “Decompiler Design” chapter really informative.
There are at least two chapters that every developer of Java or .Net applications could benefit from: Chapter 4 - “Protecting Your Source: Strategies for Defeating Decompilers” and Chapter 7: “Case Studies”.
If you are interested, Apress actually has Chapter 4 freely available.
In summary, if you are interested in decompilers and how they work - you should check this book out.