I'm looking for the best single book for implementing DirectSound solution with .NET (C# preferred). If I had 1 book to buy, it would be this one.
It can be overall DirectX, but I will only care about DirectSound.
Also, if there are any good upcoming books about XAudio2, love to hear about that too!
In all honesty I don't think there are any. There are very few books about DirectX, never mind DirectSound. Narrowing the options even further to only include DirectSound and .Net is a non-starter - they simply aren't a very good match.
99% of applications that use DirectX will be written in C++. The managed DirectX implementation was never officially supported and has been dropped now.
XNA is a different story as it's a managed API. There are plenty of XNA books, but I doubt you'll find any that deal with audio exclusively. Generally these types of books will deal mainly with the graphics APIs with audio support mentioned almost as an afterthought.
For audio programming the documentation and, to a lesser extent, online articles on sites like Code Project and Code Guru are generally the best resource.