I hadn't heard of that site, thanks! Back in 2006 or so, I was a heavy user of Addall.com for comparing prices across various book sellers. I would point people there and mention that it must be "Amazon's worst nightmare." Fast forward a few years and Amazon used books ate their lunch. Addall.com gave up so completely, their site often returns two hits for the same item, the short and long ISBN. There can't be much profit for Amazon to sell used books, but I suppose it is important to keep even the used book buyers "down on the farm."