The authors have been involved with Six Sigma methods since the initiative originally began at Motorola. In their role as trainers for those who apply Six Sigma methods, they have a bird's eye view of the implementation issues of the last few years.
The book has a nice balance among explaining the concept, how to apply the concept, case examples of application, and comparisons to other ways of thinking about providing products and services. I found that perspective was unusually broad, but pretty specific for a business book.
Three kinds of people will be disappointed in this book: (1) Those who already apply another quality improvement method and are pleased with the results they are getting. (2) People who have only a casual interest in cost reduction (3) People who would like to know the details of how to apply the analytical methods involved. If you fall into one of those camps, you should probably skim the book or skip it.
On the other hand, if you are interested in improving your operations, profitability, performance and effectiveness, you should definitely read this book. It will give you a realistic sense of what the potential is for your enterprise to benefit from the Six Sigma process. If that potential interests you, it will also give you a variety of ways to investigate the opportunity. You can't ask for much more from one book.
Separately, I should mention that some of the case studies cited here are ones that our firm has separately investigated for other purposes. In each case, the reports are identical to what we learned. The authors seem to have been scrupulously careful to get the details right -- something that seems very appropriate for people explaining Six Sigma (3.4 errors per million opportunities).
Although I like this book very much, the Six Sigma concept does have some limitations. It may help you to be aware of some of them before reading this book. First, Six Sigma is usually focused on your own operations and those of your suppliers rather than the ecosystem that supports you. This limited focus causes some opportunities to be missed. Second, there may be trade-offs between time to market and Six Sigma in short-lived products that require separate consideration. Third, many people will make mistakes in how they measure performance for the customer and end user using this concept. The author warn against this, but the concept unfortunately lends itself to being weak in this area. Fourth, the concept tends to leave an organization too complacent after achieving Six Sigma. At such moments, there are probably still important areas where approach perfection will be incredibly valuable. But your organization may stop looking for them. The theory suggests limited benefits from pressing further at this point. The theory will turn out to be wrong in some critical applications, especially where life and death are involved.
A good book to read at the same time is Lean Thinking which will give you another interesting perspective on ways to reduce defects and create more value at the same time.