This is one of the best programming books I've ever read. In terms of C# it's an eye opener. It explains a variety of rather advanced issues with a straightforward and easy to understand way. I really enjoy the step-by-step examples that show how various features evolved from each previous version of the language.
Async is a very nice feature of C# 5. I think both C# team and ASP.NET MVC team are keeping absorbing the greatest ideas from the community outside Microsoft, which makes life easier.
