First, make sure that you are connected to the internet, as the Kindle app requires an internet connection to download and open books.

Source: https://www.devicemag.com/kindle-app-for-iphone-not-working/

The first step is to download the free Kindle app from Apple’s App Store.

Source: https://www.devicemag.com/how-to-buy-books-on-kindle-app-on-iphone/

There are a few different methods you can use to add EPUB files to your Kindle app on Android.

Source: https://www.devicemag.com/add-epub-to-kindle-app-android/

This lets me use the tablet constantly during a ride in a cab or the subway to enjoy an episode of my current Netflix binge or read something on the Kindle app without fearing being left with a dead battery upon my arrival.

Source: https://www.digitaltrends.com/mobile/i-ditched-my-ipad-pro-for-android-tablet-oneplus-pad-why/