Wouldn't listen to audiobooks if they had ads.

Am surprised nobody has mentioned Libro.FM here - I get most of my audiobooks from them. They claim to give a portion to my local bookseller, though they don't provide any evidence to this effect and I would continue to use them even if they didn't. It's a monthly subscription which gives you a new book every month, but you can pause any time and the books are still around, then resume when you need more books. Your mileage may vary; the model works well for me.