As you know, Amazon has tags for their books; it helps people who want to search for books on a particular topic. The better your book is tagged, the higher up it is on their list. That means more visibility and hopefully more sales by people searching for something but without a specific title in mind.
Add your amazon link and a word to tag in the comments section of this post.
If everyone who leaves a comment tags the other books listed we can all help each other move up the ranks.