Avid Reader

I love kindle apps I had one on my Samsung recently switched to iPhone and downloaded the app.. apparently you cant buy books on this app? Thats ridiculous. Im not going to another app to buy the book and switching so I can read it. If this could be fixed that would be awesome or if Im just super confused guidance would be appreciated.

Sam Crandall about Kindle – Read Books, eBooks, Magazines, Newspapers & Textbooks, v5.13.1