Clean Reader. Sounds like something you could wipe the screen of your kindle with, doesn't it? Some kind of wet rag to get of the dirt, the greasy fingermarks - the general grubbiness?
Well that's exactly what it is. Except it goes a level deeper and wipes out the actual words. Yes - that's right. Clean Reader changes the words of the ebook you are reading.
Apparently some readers don't like swear words. Or descriptions of sex, or certain body parts. Or even words like bitch. So Clean Reader replaces them with alternatives - what it considers to be a suitable replacement.
God help us all. Allegedly bitch becomes witch (sorry, pagans), damn becomes darn, all references to sexual body parts become bottom (making sex scenes ... erm ... interesting, if anatomically difficult) and so on.
Author Joanne Harris sums it all up rather well here. And there are further posts on her blog containing emails sent to the company expressing her concerns - and the replies she received.
My books contain sex. And swearing. And violence. Because I wrote them that way. I chose my words carefully - I'm a writer and that's what I do. Sticking a filter over the top is going to make my writing at best comical, and at worst totally unintelligible. I don't want that. I don't want any app to do that without my permission, whether the actual ebook itself is unchanged or not. It's simple really - if you don't want to read what I write, the way I wrote it, then don't read my books. How hard is that?