
I thought you meant litterally, 'Clean the screen'.
It's one of these tiny things with readers that are annoying. In a paper book every time you turn a page, it's new and clean. With a reader it accumulates specks of every type, finger smuges, spittle and whatnots. I keep a lint free rag for cleaning glasses in the box next to it.
One software cutie for the reader would be to have an optional cover page of the book you're reading in permanent display.