More importantly, how does Amazon use whatever is entered there? When I import my .mobi into my Kindle reader, it picks up the ‘Title’ and ‘Authors’ as expected and uses that in the Library listing.
Does Amazon pick up and use those other entries? Would it be advantageous to put my 7 category keywords in the ‘Subject’ field, and my book description for the Amazon page in the ‘Description’ field? Would that help with discoverability? And, should I enter the ‘Publisher’ field here too, even though all of this data is entered at the KDP dashboard?
I don’t know if Amazon uses them specifically, but they definitely are made use of in more powerful readers and catalogue tools, like Calibre (which I use to manage my Kindle). It’s one of those things where even if the vendor doesn’t support using the description of the book in its store page, it’s still a good idea to have your eBook marked up well, so that it, as a file that people will buy and archive, will retain its usefulness for decades to come.
As for how best to use the fields, I would defer to MobileRead. If you look at what others are doing, it seems most publishers use Description to place the press-release or book summary (like what you’d commonly see on the dust jacket interior). I’ve seen subject used for genre keywords mostly, in fiction, and topical keywords for non-fiction.
