Well, aside from the fact that Aspen got a few of his "facts" wrong, it ain't a bad primer. Some of the stereo miking techniques are very well done.
Now Aspen is a great guy and I've known him for about 30+ years. He was the assistant manager at the original Guitar Center, then he worked for me at Acoustic Control. He started Groove Tubes and kept at it. But he's not a recording engineer. He never was. So, some of his info is based on hearsay more than experience, but he's covered most of the bases.
All in all, once you remove some of the marketing BS, it's not too shabby a primer.
A few points are kinda funny; like large diaphragm mics go lower, and his picture of the snare mic positioned in the exact center of the snare as a good spot (yeah, right). Some of his explanations as to why a particular mic is used in a particular situation are also sometimes funny.
I think the "big thread" here is a little more accurate and helpful, but his booklet is far simpler for getting a quick answer.