Amazon have changed their policies several times over the years. This is the latest missive, and should be delivered after the author loads a complete update:

Hello Lee-Anne Phillips,

Although you turned on the Automatic Book Update feature on the Manage Your Kindle, we were unable to automatically deliver an updated version of your past Kindle purchase of {TITLE} by {AUTHOR} for the following reason(s):
This book has undergone significant changes, so any bookmarks, notes, or highlights you've made will not transfer over to the new version of the book.
The updated version contains the following changes:
Significant editorial changes have been made.
You can get the updated version of this book by going to Manage Your Kindle. Find the book in your Kindle Library, click on the "Update Available" link next to the book's title, and then follow the update prompts. All your devices that have the eBook currently downloaded will be updated automatically the next time they connect to wireless.

We thank you for your business with Amazon.
Sincerely,
Customer Service Department

This is doable, if totally lame, since the first iteration was almost as easy as pie, as evidenced by the former notice from Amazon:

Hello,

We are happy to announce that an updated version of your past Kindle purchase of {TITLE} by {AUTHOR} is now available. The version you received had the following issues that have been corrected:

Significant editorial issues were present.

Before you update to the new version, check to see that all devices that you have used to read this book are connected to a network and that their Annotations Backup settings are turned on. This will ensure that your notes, highlights, bookmarks and furthest reading location are retained in the new version. For help with modifying settings, please visit http://www.amazon.com/kindlesupport.

You can get this new version by going to the Manage Your Kindle page at http://amazon.com/MYKupdate. Find the book in your Kindle Library and click on the “update available” link next to the book’s title. Within 5 minutes, any of your devices that have the eBook currently downloaded and have an active wireless connection will be updated automatically.

Alternatively, you can reply to this email with the word “Yes” in the first line of your response. Your e-mail response must come from the e-mail address associated with your Amazon account. We will update your book within 2 hours of receiving your email.

We thank you for your business with Amazon.
Sincerely,
Customer Service Department

It would make more sense to incorporate this limited user-friendly modification if they hadn't gone through an iteration in which there was no effort at all to make life easy for customers and authors.

The “Manage Your Kindle” interface is awkward and requires significant manual dexterity, so some users can't use it at all, and there is no alternative provided for the purpose of making the “Library” more accessible for persons covered under the Americans with Disabilities Act and similar legislation in other countries.