What benefit does this have over scrolling = next page? Your eyes have to refocus on the top of the page anyway, you might as well have refreshed the whole text, not just the top line of the second line.
Interesting idea though - what does this do on a touch device?
This is already standard on ereaders, nearly all (even if it's a tablet or PC app) do this. I don't like it, more than 1/3rd of the time a page turn is accompanied by a "back to last page, back to current page" as it annihilates my flow (yes, that includes dead trees).
VT100 may have something to do with this though. Straight scroll isn't optimal either. When reading long texts, I prefer to have it presented in chunks, but retain 1/8th-1/4th of the information I was already looking at in case I need to refresh where I was just now. If I can't have that, a straight scroll (bar or paper) is preferable, and if I can't have that, page to page isn't so bad either.
Interesting idea though - what does this do on a touch device?