on Just Publishing Advice:
Many ebooks and software programs can help your ebook sales through the use of Kindle keywords.
You might think that there is some magical secret that every self-published author needs to know to get ebook sales.
You can do basic keyword research without an Amazon Kindle keywords tool. There is no mystery or magic to adding keywords to any Amazon product to improve your search results and selling on Amazon.
The truth is that Kindle ebook keywords are easy to find, use, and implement for your ebook. But yes, some keyword tools can do a better job for you.