comments at a glance over:
It doesn't seem as though he is selling any "edge".
He is selling an educational book, a foundation. He seems to be unbiased, introducing basic data structures, a basic guide, and outlines a few pitfalls of developing a system. As twoshepards said, he is simply providing tools.
And as Sergio77 said, general information is free. But Van Vliet does seem to compile some useful information that someone with limited programming skills might find useful.