Every chapter is very well crafted, with a precise balance between theory and practice, and full of invaluable nuggets, sometimes transcending the MySQL arena and applicable to any database! Such cases are Chapter-Benchmarking MySQL and Chapter 3-Profiling Server Performance, very solid foundations for the reading ahead.
All over the text, authors propose tools, examples of use and proven diagnostic techniques, that will greatly improve your performance firefighter skills and enhance your knowledge of MySQL internals. Nevertheless, what gives this book the five star is taking into consideration the physical part of database structures in play when speaking about performance, which is something most authors don't include; plus treatment on MySQL high availability and cloud features, which we'll increasingly see on customers.
There is something that kind of bugged me at times and was references to a specific commercial MySQL offering and tools, but after taking a look to that company web-site, found that is a great contributor to the MySQL community and you can actually use the tools!