If you enjoy problem-solving and want to learn a structured problem-solving methodology to do that, then, Six Sigma area might be an option to explore.
There are different ways to get a Six Sigma certificate. There is no single institution that provides a Six Sigma certification service like PMP (Project Management Professional) certificate or CMA (Certified Management Accountant) certificate and many others. You can get a Six Sigma certificate from an independent institution like ASQ (American Society for Quality, your company or even an educational institution like a university.
I had to read other easier books to familiarize myself with the six sigma concept before getting into this one. I have three Six Sigma certificates; Lean Six Sigma Green Belt from my ex-employer, Six Sigma Green Belt Certificate from ASQ and Six Sigma Black Belt Certificate from ASQ as well. This book was helpful for the three of them.
The book is good and well organized. Sometimes you will feel that they have concentrated on a certain topic over another, however, you need to make sure that you really understand everything in the book in order to pass the exam.