Fair warning so you don't die
I purchased a Kindle fire to store books to read on passages and cruising information. I noticed that frequently books that I had downloaded would become unavailable due to a DRM error. The excrement hit the rotating blades on approach to Bora Bora. I could not get to any of my cruising guides as the all reported a DRM error. I contacted Amazon and was told that all of my downloaded content expires without an internet connection on a regular basis. Thus includes not only my Kindle Unlimited subscription but also things I have bought and paid for from the Amazon store. The bottom line is that if you are depending on your Amazon books to keep you safe you may be sorely disappointed.
Fair winds and following seas :)