I have had marginally satisfactory communications with Amazon in the last couple of days. Although this is not legal advice for your situation, I have posted a suggested general course of action on the main website, with a sample letter consistent with that suggested general course of action.
My conversations imply that the legal department at either Amazon or the various publishers was consulted—if at all—at only the last moment. Score another one for the marketing dorks running the publishing industry. Amazon's intransigience over the situation—denying applicability of the DMCA and stating that it wants to hear only from the publisher, due to "contractual obligations"—indicates the need for careful watching. To slightly paraphrase one of our founding fathers, "eternal vigilence is the price of copyright."
In fact, as I write this, Google appears to be spinning up its own version; and given Google's piss-poor past attitude and compliance in responding to DMCA notifications, I am not especially pleased to hear this.