I got  book yesterday but it was NOT the one that I ordered. Do I PM the sender ? i think she probably mixed up books when wrapping them for mailing. I haven;t marked the one that I was expecting as received yet. I also noticed that the one I am waiting for shows as not being delivered all the way to the end of it's journey either? Its still in the little 'truck' near the endpoint. What gives?

Check the help center on this, something like "I received a wrong book" try searchingon the word 'wrong' It will tell you all about what to do! It's probably a mix up, but the HC tells you how to proceed.

The truck doesn't mean anything, it just for amusement. It is possible that the sender printed two of your labels and you have two books on the way.  Don't mark the book as rec'd and do as the Help docs say, contact the sender and find out whats up. When you ge tthe right book, then you can mark it as rec'd. If it appears like you will never get the right one, then you mark it RWP - wrong book. 

Definitely PM the sender.  I've been known to mix up labels and send a book or two to the wrong person, but they've always been gracious about it and helped me get them resent to the right person.