*Groan*
The whole world is not against us. People are not sending spies to us all the time. The people around us are not reading our minds. Thieves don't steal random enchanted iron boxes, because they steal valuable things that are easy to conceal and transport, not heavy, conspicuous magical iron boxes they know nothing about and can't even open, and which might explode at any moment for all they know. In fact, thieves don't try to break into the rooms of Magisters at all, especially if those mages are infamous for being terrifying spymasters, and even more so to steal random metal boxes. People who might wish us harm are not omniscient. If we keep quiet, and don't tell anyone that we've read it, they won't know that we've read it. It's as simple as that.
Edit: Actually, judging by what the QM has just written, us simply having the book is bad enough, so even if we don't read it, if it gets out that we have it, we're screwed. I recommend studying it extensively, burning its contents into our minds, and then burning the book itself.