I’m very happy to see that the newest edition of Jeffrey Richter's awesome book about the internals of the .NET CLR is now available. If you have read the 2nd edition then you will already know what a fantastic resource that book is for improving your understanding of how the CLR works. The new edition targets C# 4.0 and .NET 4.0, which is coming just around the corner. (In fact, the RC for VS2010 is out now for MSDN customers, and will be available to the public on Feb 10. Check out this Channel9 video for more details)
