Not sure if this helps, but what I personally do is use calibre... then after reading a book, I add a tag called "read" to the library version of the book. It's actually quite useful 'cause i sometimes forget what the hell I read a month ago. Hell, I have issues remembering what I had for breakfast.
I don't see the use in keeping all those read books on the device itself. That's why you have library management software, (like calibre)... to manage your library. I like to keep my reader clean and simple with only about a dozen or so books on it.