I received a book with a pre-printed first class postage in the amount of $2.42 - for a package that should have had $3.04 postage on it.  The postage was printed from a site called stamps.com. Does anyone have any experience with this website?  How did they come up with the $2.42?  I paid the 62 cents postage due.

Diane

The sender probably entered the wrong postage amount, or the wrong book weight.  Has nothing to do with Stamps.com...which is an approved vender of USPS.

Did you report the book RWAP for postage due?

Yes, I accepted the book and noted that it came postage due.  I also sent a PM to the member.  I know stamps.com offers a free postal scale when you become member.  If that's the case, the member should have known what the weight was. I paid the 62 cents, but so far have not received an answer or apology from the sender. I guess that's what annoys me. 

I also received another book today with postage due.  This time the postage had been printed on August 6, 2013 and, apparently never used.  So now postal rates went up, but the sender used that old pre-printed postage on February 1, 2014. This time it was only 16 cents.

Is this an issue for anyone else?

In the first case, they entered the wrong weight, for whatever reason. You got hit doubly on postage due, because you had the difference in weight, and the difference between online rates and retail rates.