I have a background in SEO, and I've become fascinated with the algorithm Amazon uses for determining sales rank, "customers who bought this book also bought...", and for understanding what it takes to reach a tipping point - we've seen the "6 month rule" here and it's fascinating. From an analytical standpoint, we can make some educated guesses on how many books one needs to sell to reach X ranking, and we can also make educated guesses on how many co-sales you need to have with high-ranking books to be one of the featured "customers who bought this book also bought..." options.
But I also think that Amazon affiliates - people who use the Amazon affiliate links to earn about 4 to 8% of the book's sale as a commission - plays a huge role in this. I've had an Amazon affiliate account since 1997/98, back when I taught myself how to hand code in HTML and used to make $10 a month selling from it, and I still throw it on a few blogs I write.
One of the simplest features is a banner for bestselling books, that any Amazon affiliate can upload. It rotates bestsellers. Once your book reaches a certain point, it will be featured on there - not just on Amazon, but on tens of thousands of blogs and websites, in graphic form via banner.
That familiarity and exposure likely plays as big a role as the "customers who bought this book also bought..." feature, because readers may very well see the book cover 2, 5, 10, 20 times in different reader communities, blogs, etc. before going into Amazon to make a purchase. In addition, some of the widgets for Amazon affiliates let you show ONLY Kindle Books for a specific keyword.
If, as an affiliate, I want a rotating banner of thumbnails for books using the keyword "time travel romance," I can do that - and the 9-book, large banner is filled with Diana Gabaldon, but H.P. Mallory pops in there as well. It uses bestselling to rotate, so this is, I think, where a little SEO (or, perhaps, just algorithm optimization) comes in with indie publishers and product description.
If your book is one of the top selling for an obscure term, you may get into more of these banners. So making sure you have many variations of keywords might be important for getting maximum exposure on affiliate banners - which in turn could drive sales, and help strengthen you in the larger subcategories, which in turn drives up rankings and, hopefully, sales.
"Vampire time travel romance" gives nearly all indies, for instance, in the affiliate banner. "Zombie time travel" gives plenty of indies and, oddly enough, the U.S. Army Survival Manual from the Department of Defense (hmmmm.....).
Using different variations in your description might help to get picked up by very targeted ad campaigns from affiliates and help with building momentum toward the tipping point.