How to buy and download an ebook for my kindle app on iphone?

This is so different than android and i can't figure it out. I downloaded the kindle app, how do i get the book i want on there so i can read it?

The Kindle app on iPhone (and iPad and iPod Touch) doesn't let you buy books, it only lets you read them. To buy them you need to do it on the web at Amazon.com (you can use Safari on your iPhone) or use the Kindle app on an Android.

(The reason for this difference is Apple's rules about in-app purchasing, not technology).

Go to Amazon.com, login to your account and buy the books. Then you can transfer the book to the Kindle app with your amazon account.