When should I worry about a box of books going from AZ to NY showing only that electronic information was received?  I printed the label Oct. 26, mailed the 27th.  I know it's likely to not be in NY yet, but usually I get some sort of update by now(if nothing usually something about it being processed through Bell, CA)--so far nothing here.  Any advice?

The Post Office is only required to scan upon delivery.  All other scans are gratuitous.  Sometimes the Processing Center scans the DC, most times, but other times, it does not.  If it was a large box, it probably won't be scanned by the machine.  Usually machines scan the smaller/medium sized parcels.  Large or odd shaped ones can still be handled by hand at sorting centers.  I retired 8+ years ago from the Post Office and there have been a lot of changes, especially new machinery.  I have had some DCs only scanned when delivered and two not scanned at all.  But I have mailed out over 1100 books.

Give it at least two to three weeks from mailing before you worry; PBS waits 4 weeks I think before declaring something lost..  As long as you packaged it well, it will get there.

Thanks! It was a largish box--a Harry Potter Set, so maybe that's what's going on.  All the normal size, one book packages I mailed around the same time got scanned, so I was starting to worry a bit.

At least 10 days before you even start to think about worrying, then give it a few more days.  Also check USPS tracking, they sometimes have scans not appearing here at PBS.  If after 14 to 20 days the books haven't arrived and no enroute scans, check with your local post office. 

I live near a Media Mail sorting center where most of my books are scanned within 48 hours, and usually travel quickly to their final destination.  Except for the ones that don't!  Every once in a while, one will slip by the local sorting center without a scan.  A few weeks ago, one took over 10 days just to arrive in Bell (the next closest sorting center) while books mailed the same day had already arrived at their east coast destinations.  No idea why just one package from that batch took so much longer (with fewer scans), but it did arrive at it's final destination in Nevada well before going lost