I'm also hoping to release an audio version but this is quite involved and beyond my technical purview, plus I can't stand the sound of my own voice so I certainly won't be inflicting that on the world!
I've kicked the process off by creating a project on ACX that involves loading up three pages of the manuscript and specifying what kind of voice you want to narrate the book. After that, it's a case of waiting for a producer to pick it up and get in touch. I'm guessing I might have to wait a while until I've built up some eBook and Paperback sales and garnered a few reviews. We live in hope.
So, that's about it for now. I'm going to take a bit of break over Christmas, apart from tinkering with marketing. I'm waiting for another manuscript to come back from editorial review for my next book. It's not another Nathan Helix Thriller, but something different. I'll reveal more in another email. That said, I'm hoping it will be out in Q1 of next year. Then it will be time for more Helix.