Interestingly enough their own photos of reading in a dark room show a less than optimum screen, to say the least. The idea of the PW is to be able to read in a dark room with the built in light. But even their own photos show you won't get a white screen in a dark room. The upper 2/3 of the screen looks fairly grey and shadowy to me. It looks like you can only expect a white screen in brightly lit rooms and in daylight while outside.
I'm glad I returned mine. This shows that it would never look good for dark room night reading.
Amazon's own photo with caption of Dark room, light setting low [Recommended for most comfortable reading]
EDIT: Thanks for posting this great find!