Hello from Elizabethtown

I opened our letterbox today to find a lovely brown package with my name on it. What could it be? I wasn't expecting anything in the mail.

I opened it to find a book on poetry by Mary Oliver that had travelled all the way from Elizabethtown, TN. I had ordered it on Amazon, and then changed my mind when I realised it would be the same price to buy from Gleebooks (wanted to support local bookstore etc etc), and had received a refund.

So I was now in the possession of a book I hadn't paid for. What would you have done?

I did make a decision, but I'm interested in knowing what your instinct would be: a) meh it's their mistake, keep the book b) I don't own it, should send it back c) I owe them money, so will pay for it d) I should probably pay/send it back, but can't be bothered.