Yes, it’s stupid, but one of my ancient aunt’s greatest pleasure is reading, something that she can now do again thanks to a cataract operation AND her kindle with the option of goosing up the font size.
The remaining problem is she is an utter prude about ‘language’ and absolutely goes into a tizzy over not just the standard vulgar words, but author’s having their characters ‘take the Lord’s name in vain.’ I swear, she will stop reading a murder mystery ten pages from the end if she comes across one of her unholy words. 
It seems to (non-programmer) me that a program could intercept the words she finds offensive and substitute others before displaying them ought to be possible. Like you build up a chart so all ‘fucks’ turn into ‘flips’ and ‘goddamns’ become ‘gosh darns’ and the like. Or is there a site that offers books that have already been censored?
This fucking app will probably work on a goddamned Kindle, but I haven’t tried the piece of shit, so it is your ass on the line.
Is it a kindle that’s a tablet, or the eInk one? The eInk Kindles don’t run any applications but the built-in stuff, so that won’t work. Even if it’s a tablet running modified Android, if the eBooks are DRMed (bought via Kindle store or many other eBook stores), they probably can’t be opened by an app other than the Amazon Kindle app.
A plausible way around this would be to use un-DRMed books (some publishers do sell them, and there’s lots of stuff in the public domain) and run it through some profanity filter, then load it on the kindle.
Note that you’ll likely get some false positives and false negatives doing so. It seems like parsing text for a list of dirty words should be simple, but it turns out it’s not! See Scunthorpe Problem
Thank you!
She currently has an eInk Kindle, but it looks like the above reader wants Android anyway, so I guess my next task is researching an Android tablet for her. Something as simple as possible, we’re talking about a woman in her nineties. Not at all senile, but she didn’t exactly grow up with computers.
Thanks for the help!
To reiterate: I don’t believe that the above app will do what you want because it won’t be able to open the DRMed eBooks.
Yes, I saw that, sorry I didn’t acknowledge it. I’ll just have to buy books for her from sources that don’t do that DRM stuff. She likes mysteries a lot, I’ll bet the classic oldies must be available from somewhere without it.
Cool, just wanted to make sure that you weren’t going to go and buy a new tablet and then it didn’t work the way you wanted 
Kindle DRM is easily removable, if you’re serious about this. I remove the DRM from my Kindle books so I can safely archive them in the EPUB format.