Sometimes, it's just easier to hand people a user's manual instead of trying to explain things to them.
That's how I feel about inviting people over. You see, I know that people tend to react to my books in the same way they would react to someone's collection of pez dispensers, or walking into someone's home and finding a lifesize mural of Chewbacca (okay that's me, too), so sometimes I will this could be required reading before people are allowed across the threshhold.
If you are book people, this will reassure you that, while not normal, there's at least a good chance that your particular mental disorder isn't going to kill people. If you are someone who loves a book person, it will reassure you that maybe they're a little more normal than you thought.