Fast, fast, fast

I ordered a book from Amazon yesterday morning.  A few hours later I’m sitting at my computer and there is a knock at the door.  I open the door and this girl is standing there and she says "Are you Alex Tabarrok?"  I say yes and she hands me the book.  My jaw just about hits the floor.  I’m totally confused.  The girl runs away laughing.  Only later do I figure it out.  I ordered from Amazon Marketplace.  The seller just happened to live nearby and she brought the book over.  Pretty cool.