In classic Manning fashion this book is concise and focused, uses graphics sparingly and effectively, and does a great job with code annotation. The problem comes with exposition. What I wanted was a book that not only explained what JMX was, but why I would want to use it. I found that this book had a ton of technical detail, on what is undoubtedly a complex topic, but lacked much in terms of context. More how, less why.
That being said, I understand that most readers are looking for the technical side of the argument and the book has that in spades. Particularly nice chapters are chapter one, which does provide a little context for the use of JMX, and provides a very nice, though brief, overview of the JMX architecture. Chapter six, on agent notification is also excellent.
Frankly, I would love to see a second version of this book with more emphasis on use cases. For example, chapter 7, on dynamic MBean creation, would do well to cover why you would want to use Model MBeans, and not just assume the reader understands the solution out of context with the need.
If you are on a project using JMX or an architect who is already looking at JMX, this book is worth the look. If you are looking for a gentle introduction to the topic, keep looking.