This app was mentioned in 6 comments, with an average of 1.17 upvotes
The Audible app is on the Play Store and has an optional beta programme that you perhaps have entered into and forgotten about.
You could opt out of the beta programme and download the latest public build or just download the beta app again.
I've had the down arrows for as long as I have been using android (which is only a couple of months)
It looks as per hte images shown here: https://play.google.com/store/apps/details?id=com.audible.application&hl=en
I am running version 1.7.0 on KitKat
https://play.google.com/store/apps/details?id=com.audible.application
Channels for Prime -> Audiobook Collections. It's a small list, but of high quality.
The Google Play store has audiobooks: https://play.google.com/store/books?hl=en
Audible, a subscription service that gives you a discount: https://play.google.com/store/apps/details?id=com.audible.application
Overdrive, if your local public library is set up with them, it's free: https://play.google.com/store/apps/details?id=com.overdrive.mobile.android.mediaconsole
I'd try Overdrive, the free one, first if it's available.