Sure, microphones and book narrators have been around a long time. But with a $60 microphone, a computer, a bit of egg crate foam, an Internet connection, and a glass of water and we can record--and distribute--our audiobooks ourselves.
It's more than talking to your smartphone.
This is where things can get exciting with your book as a podcast as opposed to (or in addition to) an audiobook.
If you have a podcast, you have some, well, power, authority, credibility. Just like if you have a book, you instantly have some leverage...