Async in C# 5.0 (Alex Davies, O'Reilly) is good read of you plan to do parallel or async programming, although a bit theoretical. The book shows you why asynchronous programming is a little more than just using the new async and await keywords. These keywords make asynchronous programming syntactically simple, but as this book shows through meticulous explanation there is much more than meets the eye. The book starts of with just showing you how async and await works, and then shifts gear to show you how asynchronous programming worked before we had these keywords. This makes you appreciate all the heavy lifting done for you, but it also makes you understand why asynchronous programming is something you need to do with care. Then there's several chapter about what's going on and which pitfalls you can run into (and how to avoid them). The strength of this book is the excellent theoretical handling of the topic. The weakness is the lack of practical examples and a high-level view on when and how to use asynchronous constructs.