I have looked at the inkcase and I wasn't sure whether 4.3 inch is enough for reading.
A few months ago I have purchased Onyx InkPhone - 4.3 inch front-lit e-ink Android phone.
It has severe hardware and software shortcomings, yet, it is my favorite reader when I am not at home. And sometimes even when reading at home.
I can just slip it into a pocket without a case and I am not afraid that it would get damaged.
The size of the 4.3" screen is 94x56mm
The size of 6" 300dpi screen on my other reader is 92x123mm - 2.14 times bigger area for text
In landscape the width of the screen is a little bit more than the width of the 6" screen in portrait mode. With half the area for the text I have to turn the page twice as often.
Oh ... by the way ...
There is YotaPhone 2 with LCD screen AND an e-ink screen on the back for sale for $139.90
http://the-digital-reader.com/2016/0...-gearbest-140/