i sent a book out with delivery confirmation, mailed from the post office, to south carolina.

why does it tell me 'en route to omaha, ne'? do i need to be worried yet? i checked all the other books that i've shipped out and they appear to be on track to the correct destinations.

Omaha may just be a stopping point for that shipment.  I wouldn't worry yet.

It's probably a lay-over for the book.  Maybe there's a distribution center there.  I live on an island.  If I mail a letter to my neighbor it would go to the distribution center on the mainland to be processed before being sent right back here.  So it takes at least 2 days to mail something intown.