I think this is a good book for developers that want to learn ASP.NET MVC. And I think today every .NET Web Developer should learn MVC. Learning MVC will help you understand basic web concepts and even when you are developing WebForms applications you can profit a lot from that.
I like the book, because it looks a bit further than just ASP.NET MVC as it comes out of the box. With chapters about full system testing, AutoMapper, MvcContrib and NHibernate it deals with advanced topics that are neglected in most other books about MVC. The authors give a somewhat more opinionated overview how modern web applications should be created. This makes the book stand out among typical MVC books.
What I miss in the book is primarily the integration of MVC with the EntityFramework. The book only focuses on NHibernate. This was the right thing to do with the first version of MVC, however today the EntityFramework has made a lot of progress, and in my opinion it should be considered the default choice for ASP.NET MVC.
If you are already familiar with ASP.NET MVC or have even read a previous version of the book, don't expect to learn too much about the new features of MVC 4. Only the last two chapters of the book deal with specifics of the fourth release of the framework (probably the book was initially planned for MVC 3, but the fast release cycle of the MVC team made the authors skip directly to MVC 4).
Nevertheless, for developers that want to learn MVC, I think this book should be a must-read.