One of the problems with something like architecture is that it's difficult to quantify the value. This is even more difficult when the approach can be applied in many different ways, in many different circumstances. This is certainly the case for MDA. Perhaps the best we can do is point to examples of how it is used, where it's been successful, and what value it has contributed. Well, if you want to answer those questions for MDA, this book is for you.
Real-life MDA, as the title suggests, is basically a book of case studies. Each case has a similar structure describing the problem being addressed, why an MDA approach was chosen, the goals, the challenges faced, how MDA was used, what processes and tools were used, the results and benefits, and the client's assessment of the MDA experience. But that's where the similarity ends. One case show MDA in an Agile environment, another highlights MDA and code generation, another shows how MDA is used to create Enterprise Architecture, yet another shows an MDA approach to outsourcing. This illustrates the variety of MDA approaches, while providing a framework to understand and compare the different examples.
I should of course mention that the book is easy to read, in spite of the non-trivial nature of the subject. Both Guttman and Parodi are excellent writers who keep the flow interesting and insightful. If you've thought MDA sounded good, but couldn't articulate the value, now you'll be able to. If you never quite bought the idea of MDA, hopefully this book will change your mind. In either case, you'll enjoy the read and learn something in the process.