…the USPS employee or contracted worker located somewhere between northern Indiana and Nashville, TN.
Ahem.
I think I’ve figured it out. I think I see where you were coming from.
There you were, unloading or loading a truck, or maybe guiding packages down a belt or something and you see this fairly good-sized box. It’s marked “media mail” so maybe you thought, “Ah-ha! DVD’s! Video games! A box full of ’em!”
So then you took out the box-cutter you’ve got on hand for just these occasions, slit the bottom of the box, let the contents fall into whatever bag you’ve also got on hand for just these occasions, whistled and waited for the next box.

I suppose you really didn’t actually have a chance to handle the box and see that it weighed a lot more than it would if it were, indeed, filled with DVD’s or games.
Because, in fact, it was filled with,you know, books.
And speaking of books, I HOPE YOU ENJOY THOSE 40 COPIES OF PROVE IT CHURCH MEANT FOR KIDS BEING CONFIRMED ON FRIDAY  IN NASHVILLE. I PARTICULARLY HOPE YOU ENJOY READING THEIR LITTLE NAMES INSCRIBED IN EACH BOOK.
Yeah. Enjoy. And while you’re at it, prove this.
(Okay, okay. Here’s hoping the criminal, upon opening the stash of 40 stolen books about God takes it as a message and changes his or her ways. There’s a purpose for everything. Got it.)
(And yes, it was insured. And yes, the box was indeed delivered empty, with the bottom neatly slit open.)