Fascinating. That's this book:
https://www.amazon.co.uk/dp/B08XZS8VMW/
Which is published by Penguin and appears to be a simple novel. And yet for some reason it insists on having the latest version of the Kindle app.
To avoid the irritating KFX format, you could try method 2 of the first page of this thread. Or if you had an E-Ink Kindle, you could try download and transfer via USB.
This might be a sign of some publishers trying to up the ante on DRM.