Amazon book updates

I have been in contact with Amazon about automatic updates of books that you may have loaded to your Kindle. I am still a little confused as to what is going on. Yesterday when the file for Duplicity was live I tried to update my device and received the same old version of the book. Then I waited all day for the system at Amazon to do the update after first going to my Amazon settings and turning on Automatic Updates. This setting is to allow your Kindle to receive the updates. If this is not turned on you will not get them.
At about 4 PM I called Amazon and asked them what was the problem. Come to find out that no it will not work on some units sold. So the long and the short of it is if you are looking for the updated book and your Kindle unit will not deliver it, call Amazon. They will then send it to your device. Takes about 5 minutes.