I recently finished reading...
I have been wanting to get in to the world of WCF for some time now, but wasn't really sure how to get started. This book was good at explaining how to get into WCF quick and easy. The sample apps that the author goes through and provides are pretty cool which makes it more fun.
The book explains how data binding in silverlight (which seems to be similar to how it works in WPF), how to pass objects across the wire using WCF. It explains what RESTful services means, and how to build them leveraging tools on the .NET stack.
The sample apps include one that consumes Amazon's RESTful services, as well as a Twitter client called SilverTwit. There's lots of code to dig through, and try out for yourself.
For anyone interesting in Silverlight or WCF, this is a good book to get you started.