Over the past year, I've made updates and/or corrections to most if not all of my novels (listed below). According to Amazon, "You should get automatic updates if 1) your device is connected to wireless internet (Wi-Fi), and 2) you turn on automatic book updates. To turn on automatic book updates:
Go to Manage Your Content and Devices [this is the link I get on my own PC, if it helps: Amazon instructions]
Click the Preferences tab
Scroll to Automatic Book Update
Choose On
If your book doesn't update automatically, contact us. You won't need to buy the book again, but you might lose notes or highlights."