For as little as 30$, I'll recommend your free romance book to my email subscribers in a Solo newsletter. Solo means that your book will be the only one in the newsletter. It will not be competing with other books for clicks.
This newsletter has been running for over 3 years with more than 3,000 sent to date. My subscribers eagerly await emails, always seeking new authors to subscribe to & buy from. They have been a significant factor in turning my books into Amazon #1 Best Sellers multiple times. Check out the results that other romance authors have experienced.