Audio has been around since, I suppose, the spoken language. The difference now is distribution and availability. Audiobooks, podcasts, smart phones, voice controlled home speaker systems, connected cars, and who knows what will come next.
This is where things can get exciting with your book as a podcast as opposed to (or in addition to) an audiobook.
You have audio. You probably have a book cover. You're all set. Using an online (and mostly free) tool called Headliner, you can easily...
When I first opened the Audacity program I have to admit I was intimidated.