I just did a test on the inverted in the closet.
It only refreshes, which then is whit-ish once in a while. I kept counting, one time it was 25 pages, then it was 20, 15, etc.
Until I figured out it refreshed every time there was a new chapter starting.
It is a very brief "flash" and even though my eyes are sensitive, I didn't really notice it much. Its not glaring, I had the light at 9 by the way for that. The lower the light, the less flashing there will be. But its only every so many pages. 20 or thereabouts. Not sure about the book that doesn't have any chapters.
The flash isn't any more bright than if you read on normal mode in a dark room and what the backround is then.
It didn't bother me, but I couldn't read with a black backround anyway, my eyes don't like that.