As some of you have noticed and inquired, ZBookStore and Bookapy now have featured books on the home page.
You can purchase those spots for your own books.
The author panel on the site allows you to buy those spots for a day (or more if you wish).
I didn't build a way to pay for those with a credit card. You can only pay from your wallet. And it allows negative balance, so you can buy a spot with no money down and it will get paid from your sales.
https://zbookstore.com/author/purchase-featured.php
The system does not allow adult oriented books to be featured on bookapy.com.