Okay, THAT I can understand (background-wise). In normal lighting the contrast is not near what it looks like in ad photos. Outside or in very bright light it can be close but in normal light....no. Unfortunately for your needs, all the standard e-ink displays are lacking due to normal use contrast issues. It sounds like you really need something with a good backlit screen which leaves current e-ink devices out of the picture.

Right now (as far as I know) all the e-ink devices will have excellent typesetting with contrast levels of "meh" due to varying degrees of gray making up the background. This makes it fine for people ranging from good eyesight to distance problems (since the fonts can be enlarged as needed). For dim vision a display using more contrast is usually needed (which is where a nice LCD screen is very useful).

If you can, take a look at the Nokia mentioned earlier too. It's cheaper than the Sony but being backlit might provide a better reading experience for this situation. A plus is that they are easy to find in any major electronics store.