"A new version of the Play Store is rolling out, but you're probably not going to see too many changes outside of a couple different banners here and there. However, a teardown of the APK does provide quite a bit more to look at. There are clues suggesting the Play Store will soon begin selling audiobooks ...."
http://www.androidpolice.com/2017/11...-apk-teardown/
So, how will they be played on a mobile device? Google audio books that is, what app will you use?