I chose this instead of the weightier Desk Encyclopedia, also published by Amacom, to supplement MCSE study materials and the New Riders Essential Reference for the Core Exams. There is very little I haven't found (a few odds and ends of acronyms), but it has very good illustrations and charts of many concepts that can be extremely arcane. It will even take you back to the early days of computing, and includes cites for a number of vendors who met their demise in the 80's and early 90's. Remember the PC/jr? It's in there.
This is an excellent resource for those whose knowledge of the field extends from basic to excellent, because it's hard to believe that anyone (well, okay, may a few...) could possible stuff all this stuff in one brain.