The Nook had a high resolution screen, a lot higher than the Fires, etc. I forget just what that resolution was but it was an excellent screen for text. Fires are pretty poor for text and so are most cheap tablets, even name brand ones. They tend to have the very low res screens that the Fires have.
Have you considered an e-ink reader. They're better for reading although they're pretty worthless for anything else.
Another thing to consider, as long as a small screen doesn't bother you, is a cheap smartphone. I've read a lot of books on phones that I bought for just that purpose. My most recent one was a Motorola Moto E 2nd generation that I bought from Amazon for $40. I didn't use it as a phone and I never got service. I used it simply for reading. It has an excellent screen and everything worked beautifully.
I stopped using that for reading when I got myself a real smartphone for phoning. I recently got a Samsung Galaxy S5 on sale for $200, brand new, and it's now my smartphone. It has an AMOLED display instead of LCD which is much gentler on my eyes.
I prefer to read on e-ink but when I'm away I'm glad my book is on my phone.
Barry
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