Dr. Richard Grimes does an excellent job of covering the world of DCOM - automation, security, threading models, NT services as COM servers, MTS, debugging DCOM servers. Everything I need to know about the ins and outs of DCOM is in this book and it is covered in a professional, thorough manner.
Note that Dr. Grimes does not cover the tools and techniques for writing DCOM servers (ATL, MFC, VC++), but it is as well that he shouldn't have - that would be distracting and draw focus away from the more challenging tasks addressed by Dr. Grimes. Tools and techniques should be covered separately (as well they are).
In addition to all of the DCOM architecture, design and implementation gems covered, I use this book exclusively as my "other-than-Microsoft" reference to MTS. In one chapter Dr. Grimes performs a superior effort in coverage of MTS than is done in SAMS' Microsoft Transaction Server 2.0 (Roger Jennings' Database Workshop), a book entirely devoted to MTS.
I look forward to other such efforts of Dr. Grimes being published.