Rather than have pop up menus obscure the text you are reading, this concept design puts the menus in the margins.
As explained on the website, the menus would only appear if you double tapped the margins. I believe that is intended to let you also use the margins for page turns (a single tap), but I suspect that in practice users will regularly bring up the menus without intending to.
The designer has also posted images of a dual screen design that would place the menus on the hinge between the pages:
I think that could end up being a lot less convenient, not to mention more expensive. The dual-screen concept would require 3 screen elements, raising costs even higher than for a simple 2 screen design.