Depending on what kinds of ebooks you are reading, you could try out
HackedUpReader.
With HUR you can customize what part of the screen will turn a page (left/right half or top/bottom half of the screen).
But HUR doesn't support DRM and the specific Kindle formats like KF8. If you only read non-DRM epubs, fb2, or some other supported formats, you could give it a try.