I broke my rule recently yet again and purchased a "new" book on Amazon from a third seller that was about 1/2 the price of any Amazon shipper for the same item. When it arrived the book was not only not new, but was seriously damaged. Pages were all stuck together where the book must have been wet at some time, a bunch of the pages were torn. This thing was damaged so badly that I about 1/3 of the pages aren't even readable. I contacted the seller and they told me they would send a replacement "right away". That was a month ago and still no replacement, but they have a "no refunds" policy.
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Here's a picture of this "new" book. The packaging was not damaged at all so this had to be an issue with the reseller rather than USPS.