Having worked with both products,individually, it was nice to find published work on the collaboration of Sharepoint and Silverlight. The text is an easy read and the examples are well described. If you're new to either of the technologies, this is the book for you.
My only criticisms: the cover price was too high. I understand that the authors have no control over that, but wrox needs to be realistic when pricing their books. While the content of the book was good, I wouldn't say that there was enough material to warrant a $50 cover. Amazon has it for $31, but i bought mine at the local Barnes and Nobles. Obviously, the convenience offset the cost difference, but I felt the book should have come in at a $40 cover.
Also, there is a lot of huge screenshots and unnecessary code listings in the book. If you were to shrink the shots down and pull out the VB code (leaving C#), this book would probably run about 200 pages. Here again, including the VB code alongside the C# code may be a Wrox thing, so I didn't let that affect my rating of the work. When I published through Apress, I was fortunate to have the option of not including both languages.
Overall...a great book and definitely a worthwhile addition to your tech library.