Depends, Holy Books are as powerful as the faith their believers put in them.
Secular books are only powerful when they're focusing an already popular idea or set of ideals, though said ideals don't have to already be organized and knowingly widely popular.
As to the PoD Book itself, well Pan-Germanism had enough issues itself, ranging from large groups of the general population opposing it to the ruling powers opposing it to its supporters torn and opposing each other on what form it should take, and that's in a cultural zone where everyone speaks the same language and had spent a millennium as part of a single polity of one sort or another, so yeah, Pan-Germanicism is never going to be popular since their were already established national identities and neither the populace or governing powers would be supportive of it, regardless of how charismatic a book might be written.