Well yes, in fact, I have read a book on my 6+ using the Kindle app and I love it. It is so much better than reading on my previous iPhone 5. The 6+ "disappears" when I read just like when I read on my Kindle Paperwhite, not so with the 5. However, I have decided to keep my Paperwhite for when I read outside with the glare of the sun or if I am in situations where it would be too risky to use the more expensive 6+ like if I am sitting in a jacuzzi or something. And because I am keeping the Paperwhite for those reasons, I am probably still going to use the Paperwhite at home and use my 6+ when out and about as I do still prefer the Paperwhite over the 6+, but I will occasionally grab the 6+ at home too, which I never did with the 5.
thanx, that's £169 in my pocket; 6+ will do the job perfectly!