I bought three travel guide books at Amazon one the same day. Two of them I wanted to take in my upcoming trip, so I paid more for a faster delivery. The third one I don't plan to take with me, so I purchased with a cheaper delivery fare.

The third one arrived, the 'urgent' two ones not yet. The expected date is not due yet (May 17th), but it sucks to receive first what costed less, and I can now only hope the most important ones arrive on time!