I bought this book having grasped the basics of COM and IDL and expecting it to help me improve my designs and better understand the issues in how to develop a "good" COM interface.I found to be mostly disappointing from a design standpoint. Many issues which six months later I had learned were really very important (e.g. the vital question of whether to support IDispatch or not and the huge performance penalty in MFC's default use of this interface) were not covered. There are many trade-offs in COM and I found little discussion of them here.As a reference it has potential, since it is thorough and deep, but as other reviews have mentioned, it's not as easy to use as a reference as it perhaps should be.In the end, it's been sitting on my shelf largely untouched as other ATL and COM books become dog-eared with use. So from me, it's thumbs down.