I just submitted a suggestion to AMAZON.com - wonder if they'll take my advice? I think they should allow account holders to create a library reference on their website so we can track our books already owned. Not only would this be beneficial to ME so I do not duplicate purchases (hate it when that happens!) but it would give them insight into their consumers as far as what subjects & materials they invest in, regardless of where purchased. Win-win for all.
Personally, I think it's a brilliant idea!