I still go back and dip into Essential COM now and again. I bought my copy because I was involved with a project to build a COM/CORBA bridge and needed to get my head around COM's infrastructure. Also back in the day I used to write a lot of code that ran under Microsoft Transaction Server (MTS) and COM+.

Another interesting book by Mr Box and co-authored by Chris Sells, purely from a historical perspective now as it's fairly ancient, is Essential .NET Vol. 1[0]. Sadly they never got around to writing a second volume.

As a humourous aside, who remembers Don's lecture he did from a bath tub?:

https://blog.mattmags.com/2011/05/19/don-box-the-bathtub-lec...

[0]: https://www.amazon.co.uk/dp/0201734117

Definitely Don Box's Essential .NET (http://www.amazon.com/Essential-NET-Common-Language-Runtime/...). For the concurrency aspect I recommend Joe Duffy's Concurrent Programming on Windows (http://www.amazon.com/Concurrent-Programming-Windows-Joe-Duf...).