Starship running on mushrooms? Yeah, why not
The mushrooms are some omnipresent thing connecting all space and time together and giving some special super powers somehow? The force stolen you have. Integration of science fantasy into science fiction unasked for was.
Regarding the sources for books, you've gotten a lot of recommendations already. Loading them onto the kindle is super easy. You cannot only transfer via USB, your kindle even gets it's own mail address you can then just mail your books to and have them converted and transferred by Amazon.
Meta has this dangerous mentality that they are above the law anyway, so whatever they say, until a government powerful enough to really make them pay steps up and shows them that they are in fact not above the law, they'll just fucking do whatever they fucking want.
Yeah, okay. So: Clearing Browser cache is a common feature in any webbrowser (even Chrome, and if Chrome has it, everyone has)
Regarding insights into the local cache: Are you technically versed enough to understand what you are seeing? If not, what good would looking at the cache do to you? I mean, whatever is in that cache is no indication about your privacy at all. As @minitycactus found out, Wikipedia logs your last visit. Do they spy on you? Very probably not. Besides, whatever they put into local cache is not something they have on their servers,
I wouldn't put too much energy into a search for that specific feature.