Yeah, the ISBN is pretty neccesary - that's what all the booksellers use as the product ID in their systems. A DVD would probably need one too, or at least some bar code number.
The most difficult part... hmm... there are really two:
1. Amazon doesn't do product updates. I'm working on the second edition of my book now, so that's something I'm currently dealing with - if the second edition has a new ISBN (as it should, under ISBN rules), then people searching Amazon will end up finding an (eventually) out of print edtion right away - placement in their search depends on sales. So the not-available copy might rank 5 in your search terms, and the new and improved ranks 2,000,000. They will not cross-reference. If I break the ISBN rules to maximize sales with Amazon, I tick off all the other distributors. If I follow the rules, Amazon sales won't capitalize on previous reviews and promotions. Definately a weak spot in their system.
2. They do things their way. My book packs 35 to a case. If Barnes & Noble wants 108. they order 105 or 140. Amazon orders 108... ship it or else. I've had weeks with FOUR Amazon orders - you'd think they could bundle them up and save me some postage? I've pointed out that their re-order system sometimes does whacky things... order 40 on Monday, 1 on Wednesday, 35 on Friday.... their response is pretty much "ship or orders, or cancel them and we'll take you off the vendor list"
On the plus side, they pay fast, and by direct deposit. And if they lose books they own up - I had an invoice go past due, they said they never got it, I sent proof of delivery, and they paid right away. That doesn't happen with other distributors.
Overall, they're a great customer.
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