This is a great book for someone looking to get a broad view of the Silverlight 4 platform. It is very simple to read/understand for anyone wanting to get started. The book is very illustrative – literally – to provide good visuals about each of the core concepts. At the end of reading this book and following the examples, the reader should be able to quickly start building “real” applications using the basic concepts.
For an advanced user, which I don’t believe this book targets, it is missing some of the more larger aspects of deeper databinding understandings/techniques, development patterns (i.e., MVVM in depth), richer styling/templating of custom controls. Again, these are not what I’d consider fundamental to an introductory and as the book points out — it is helping you learn by having some fun with Silverlight 4.