I bought and read this book about 16 months ago.
I've re-read it twice since then. This is not because I didnt understand the book the first time -- its because there are so many layers of information in the book.
Some authors seem to be able to write 20 books on a subject -- You've seen the authors that do 3 C++ books a year, or 3 COM books a year. This is great for publishers, and the successful "serial author". (I am aware that Stroustrup has 2 other C++ books and Don has taken part in Effective COM -- but they're not on the same subject material)
Don takes a different approach. He's only going to write one COM book and do it properly. He does. This book is the most dense in terms of giving solid information to help you understand whats going on. Whats going on when your product is about to ship and there's only 3 "showstopper" bugs left. Thats when understanding it properly matters. It also matters when you want to design something. These details also matter to VB projects when they ship, or when they're being designed.
I generally read any COM book I see sitting around. So I've probably read about 6000 pages on COM. I've seen about 1000 wizard screenshots. I've seen 40 analogy-riddled COM explanations. I've seen "cute and funny" examples. This is the only one I've bought and I've never regretted it or covetted my neighbour's book.
Similarly with C++ books, there are authors who sell a rehash of the same material 20 times. I read any of these lying about too -- another 10,000 pages with 50 useful per book. I only _bought_ Stroustrup.
It's not (nor was it intended to be) _the_ tutorial. It doesnt have screenshots. Its not 'funny'. Depending on your initial level of knowledge, you should probably read one or two other books such as Inside COM (or intros to other books of that ilk) -- in fact the best primers are probably articles in MSDN. Use these as a primer as necessary. When you've read 1500 pages of these, come back to Essential COM, and you'll have any gaps in your knowledge filled in.
If I was allowed to own only 3 books on C++/COM development, they would be Stroustrup, Box and Effective COM. (Although Mr Bunny's Guides would come close :)
Finally, would people, regardless of positive or negative opinions held, please be kind enough to give their identity -- IMHO it invalidates your opinion if you're not willing to stand behind it.