I am very sleepy and had capoeira today so I am even sleepier but as far as I can tell from working in shipping for ten years, when weird crap like this happens it's usually because a box popped open in transit and then they scrambled to shove things into another box, sometimes regardless of whether or not it was the original box.

This leads me to believe, depending on what books Suz got, that maybe your box got swapped with a Priority box, but the label on the priority box popped off so they figured "hmm, greek books, this thing, must have been this package."

(This may not actually make sense, I'm going to go to sleep and try and apply some shipping experience to it in the morning. Alternatively, Hermes is having a laugh, which is also possible.)