Amazon’s other options for me is something called a Sponsored Ad. My mentor/author didn’t think much of using these, but I bravely tried the concept of picking keywords from my books and bidding for clicks. Every time, it failed miserably, but the good news is if hardly anyone clicks on your ad, it doesn’t cost you much.
A little poking around showed me I had another choice called Individual Products. It involves picking products (books) similar to mine, and advertising to those who buy them. It took forever to seek out these books, although it probably was a good exercise for me to get to know more about what was out there. None-the-less, all this effort yielded even fewer clicks and cost almost nothing.
Then recently a new option emerged. I could bid to advertise based on genre, just like with my Lock-screen ads, but the ads would appear to all Amazon users. So I tried it. And oh my goodness.
Read more at Where did all those genres come from??