Deeply Understand C# and .NET Framework

I think it is important for developers to know more about deep and low level aspects of their favorite Framework/Library.

For .NET developers this thing is extremely important as they can easily mess up design and code of their programs. Plus, the more you know, the less you face unknown problems

As a matter of fact, I started reading these two valuable books about Advanced C# and .NET Framework programming.

PS: Thanks to MMR for recommending me the first one.