LibriVox is a service which provides open AIP hooks for apps that can read their public domain audio books for free. Zero. Zilch. Nada. You can check out their catalogue at…

https://librivox.org/

and find an app for your phone at pages like…

https://librivox.org/2011/11/09/iphone-apps-for-librivox/ (for iPhone)

or
https://play.google.com/store/apps/details?id=biz.bookdesign.librivox&hl=en

Either way, you’ll find zillions of free books, including “The Deeper Christian life,” by Andrew Murray.