You sure he was talking about your book?
I looked at a couple of his other reviews (it's obviously a him), and I think he probably likes the fact that you retain the importance of a real military power even in the face of magical powers. You don't discard everything else as unimportant/pointless/useless - which tends to be what happens in many books that include magic.
ETA: I'm not familiar with Scalzi and how his work may relate to this comment.