Facebook and Instagram, and sometimes Twitter.
Facebook works for discussions over things you want to share regarding your business. If you interact (not just post, but talk to people under your posts), it works. Otherwise, it is just a time loss. One of my music projects has 6.5k or so followers, and the interaction (from likes to shares to comments) is around 5% whenever I post something. That is a good number, considering that most translate into 1%. However, the dynamics of a music crowd is different than of a reader crowd. You have more audio-visual content to stimulate people.
Instagram, on the other hand, works better to reach out unknown people through #hashtags. Of course, it creates the necessity of taking pictures of me, or my surroundings, or some stuff that I like on a constant basis to create content, especially about writing as it is not a very "visual" art. I don't like taking pictures, so it is a challenge.
I need to hire a marketer for myself, and an assistant. Yes.