If you can only read one book this year: Professional C# 4 and .NET 4 from wrox is the one.
I just read the Professional C# 4 and .NET 4 from wrox, wrote by Christian Nagel, Bill Evjen, Jay Glynn, Karli Watson and Morgan Skinner. This is a complete book in whats in .NET 4 as well as a great book for anybody jumping in .NET. They did a great job including all the important parts of .NET as well as the new version 4. As I was reading, my first impression was how far .NET has gone since version 1.0, the different platforms including WPF, Silverlight, ASP.NET ADO.NET, LINQ and PLINQ now...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.