You can add a @page margin that will allow you to read ePub books without the broken part of the screen being used. To see if this approach is suitable you can test it by adding line like this to the book's stylesheet (add it to the bottom of the stylesheet so that it overrides any @page margin set by the publisher):
Code:
@page {
margin-top: 40mm;
}
Adjust the 40mm length to match the size of the broken part of the screen.
If you find this is workable for you, then you can either set up Calibre to add the @page margin to the stylesheet automatically when you sideload books, or I can help with a firmware patch that does the same thing without needing to edit the books. (The only advantage of the patch is that it works with DRM ePub books too.)
Although this method should work to restrict the content of the book to the working part of the screen, it won't help with the TOC, dictionary, top menus, etc. It also won't work with KePub books.