I have been surprised at the sales of the audiobooks. All I have to do is promote my novels as I normally do, and the audiobooks tag along, sometimes outstripping the ebooks in dollar sales, if not actual numbers (since audiobooks are more expensive than ebooks).
It’s part of the massive learning curve of having to promote my fiction rather than leaving it up to a traditional publisher who might be incompetent at the task, or who doesn’t care (sometimes both). I may not be great at promotions at this point, but I’m better than I was at it, I’m still learning, and I definitely do care.
Here’s a question and answer bit I did at a website concerning my superhero novel, WORKING CLASS HERO. I’ll be adding the second book to that series very soon, and have plotted a third book. If sales and/or my desire to continue warrant, I’ll be doing more in that series. I like the characters and I enjoy the act of creating new stories in that world.