If it was planted in some way, it'd make more sense for the contents to be clear instead of some ambiguous note. But the fact that they're not trying to confiscate it probably means it either benefits them to have us know this or they're just indifferent.

[He'll move to pick up the book and flip through the pages thoughtfully.]

Anyways, if no one else wants it, I'll take care of it for now. Feel free to grab it from my room if I die.