Thanks very much, a lot to ponder on here.
Once I'd started on my Paperwhite I felt that I hsd reached the pinnacle, until in my move to use ePub I acquired a Kobo Mini, which does not have a lit screen. As long as I had an external lighting source, it seemed better, and I was able to read for longer periods of time. Then I reverted to Kindle Keyboard, and again found it all very soft and relaxing. As I want another ePub reader, I'm thinking of acquiring one of the Sony models next, as owners seem to love those.
Thank you, Katsunami, about your experience of "front-lit" screen. That's what a Paperwhite is, is it? Am not quite sure of the difference between front-lit and back-lit really. Anyhow, that's a really good idea about turning the light down to zero, and then up till you
just notice it. Good idea! I might try that, and could even try in combo with an external ereader light.
Experiment, experiment, experiment, that's the thing, but Hey! I have to get back to my book!

Regards,
John