Kindle Automatic Update Dec 2017...
One powerful aspect of Kindle books are the 'Automatic Updates' to any purchased books in your library (you can check this is enabled under Settings in your device/app) to ensure your books do have the latest versions or revisions, made by an author. (This is also under 'Manage Your Content and Devices' in your main Amazon website settings.)
Both 'In the Spiral' and 'Fountellion in The Spiral' have been revised a lot since initial publication, or to improve readability on kindle.
Authors: would expect this to be an automatic process in the KDP publishing tools (which are otherwise pretty good), every time we make a decent revision, or at least that we could have control of that option.
Actually, I've just discovered that we have to contact the Support team in order to 'push' any revisions via Amazon who will then notify the readers with your book on their app/devices.
Well, I've now done this, so expect to see some sort of notification, so you can update to December versions of these books (see also under 'Manage Your Content and Devices' in your Amazon website settings).