Buy Kindle Books on iPhone & iPad in Seconds: Learn How to Organize your Kindle Library, Gift Kindle Books; Including how to use Kindle unlimited (Paperback) - Walmart.com
You can't buy books via Kindle Android app, but there are a few solutions
You can no longer buy Kindle eBooks on Android - Good e-Reader
Amazon updates Kindle for iOS with iPhone X and 10.5" iPad Pro support
Amazon Fire HD 8 (2020) review: A tablet for Amazon lovers, and no one else | Mashable
Kindle for Android:Amazon.ca:Appstore for Android
Amazon Kindle Fire HD 7" Reviews, Pros and Cons | TechSpot
Amazon Kindle Fire redirects all Android Market requests to Amazon App Store - The Verge
The ultimate guide to using Kindle app for iPad and iPhone
15 essential Kindle Fire apps (pictures) - CNET
Kindle for iOS Redesigned with Clean, Streamlined Organization - MacStories
Kindle Fire 7 Tablet, 7" Display, 8 GB, Black - Mantis
Free Kindle Reading Apps for iOS, Android, Mac, and PC
Best Kindle Fire Apps
The ultimate guide to using Kindle app for iPad and iPhone
A Look at Amazon's Redesigned Kindle App for iOS and Android
How to Read Kindle Books on an Android Phone/Tablet