You can't buy books via Kindle Android app, but there are a few solutions
How to Buy Kindle Books on iPhone & iPad (2023)
Kindle Unlimited UK - Get Kindle Unlimited Books for Free without Kindle Unlimited Subscription (UK Edition) eBook : Natch, Lavee: Amazon.co.uk: Kindle Store
How I sell Books on Amazon KDP: Step-by Step Picture Guide on how you can sell lots of books on Kindle (Book Publishing and Marketing) eBook : Oguntade, Sesan: Amazon.co.uk: Kindle Store
Amazon Kindle Fire HD 10 User Guide: The Complete Manual Book on How to Master Your Kindle HD 10 Tablet eBook : Allen, Carlos: Amazon.co.uk: Books
When did this happen? Can no longer buy Kindle books in Android Amazon app? : r/kindle
Amazon will not allow older Kindle users to browse, buy new books
How to read Kindle books without a Kindle
Which Kindle Should You Buy?
How to Put Free Ebooks on Your Amazon Kindle | PCMag
Amazon's new Kindle for Kids is probably not as good for kids as real books | MIT Technology Review
How to Buy Kindle Books on the iPhone or iPad - YouTube
Here's Why Amazon Won't Let You Buy Books on Kindle App for Android Anymore - CNET
Kindle buying guide
How to buy books on Kindle | ZDNET
How to Buy Books for Your Kindle: 7 Steps (with Pictures)
Why You Can't Buy Kindle Books in the App & How to Navigate the New Platform
Why you can no longer buy e-books from Amazon on Kindle app - Wales Online
The best free Kindle books to download now
How to Buy Kindle Books on iPhone & iPad (2023)
