I've wrapped my head around most of Essential COM by Don Box, but it is a tad outdated and full source that is supposed to exist is quite awol. (No included CD, linked to a website, which of course 8 years later doesn't have the files)
There is also a general gap on things I've been reading and my own understanding about what divides OLE, COM, DCOM, and COM+. Let alone when ever I go looking for information about IDL I mostly end up w/ information about Cobra's IDL and not MIDL.
I'll be cramming again this weekend on it, and hopefully have some results soon. I apologize again. So far sucking pretty hard at this article voting system. :P