The third group is focused on counterintelligence and security. I think the reason for that is fairly evident, in terms of vulnerabilities of the department and the harm that can come to it by failing to detect when we have, in fact, been harmed.
I don't think anyone wants a reader to be completely lost - certainly not to the point of giving up - but there's something to be said for a book that isn't instantly disposable, that rewards a second reading.

