Paid ads are way too expensive so I made my own. I create the posts in PowerPoint or Word but if you have friends with better skills, create better ads.
You might be asking how I came up with the ads? It's easy. Look at ads for books that you like and come up with your own take.
These are a few of my favorites that I created and posted on Facebook. Word to the wise, only use images that you create or that are public domain.