The Amazon app will only let me download a sample for Kindle. There’s no longer a button to purchase a book. I’ve bought many books for Kindle before. What’s up?
Are you using an iDevice? If yes, you can't buy from within the app. Use a browser to make the purchase and have it delivered to the app.
Apple wanted 30% of the sale, so the ability to buy from within the app was removed by Amazon.
When you're in up over your head, the first thing to do is close your mouth.