You simply download the app and then you can read any ebook you purchase through a "cleaner" lens. You buy books right from the app, which is why they are able to offer the app for free. So if in-app purchases are a problem for your kiddo, this might not be for you.
I can see the value in this for kids. My daughter is a middle grade reader whose reading level is above what is generally marketed towards her. There have been a few books that I may have considered if I had something like this.
More often though, I see a problem with content for age. So the problem with this app, for me, is that if there is frequent profanity, etc., there is usually going to be a content problem as well. I think this could give parents, teachers, and readers a false sense of security.
From the author's point of view, it's even trickier. Is this just a form of censorship? How can we be sure that the author's point is taken if the words have been changed? Think of
The Adventures of Tom Sawyer, for example.
Mark Twain used offensive language, racism, and lots of tomfoolery that would probably be edited by this app. But in doing so, are we missing a lesson in historical world view?
What do you guys think? Would you ever use this type of app for you or your children?