I've definitely noticed this when travelling on the tube. At one time, lots of people had Kindles - especially young people - but now those who are reading are generally reading a paperback.
I think it's great - books have so much more character - and you can give them to friends and charities when you've finished with them. Also when they're finished with they can be recycled.
Ethical Consumer doesn't really come to a firm conclusion:
"E-readers require the mining of a whole range of non-renewable minerals like columbite-tantalite, which is used to make capacitors.[5] And at the end of its life, if your e-reader ends up being ‘recycled’, the chances are it will end up being dismantled by hand in a developing country where workers and the environment will be exposed to a range of toxic substances.
"At the same time, paper books are not innocent on the toxics front. The production of ink for printing releases a number of volatile organic compounds into the atmosphere, including hexane, toluene, and xylene, which may contribute to a range of public health problems.[6]
"Comparing such different impacts is obviously difficult. A paper by GreenPress concludes thus: “[The] “breakeven point” will be different for different metrics of environmental performance but...for greenhouse gas emissions this number is probably between 20 and 35 books while for measures of human health impacts the number is probably closer to 70 books.”[7]
"So overall, the best information available at the moment suggests that e-readers may sometimes be able to beat paper books on environmental impacts, but only if you read on them a lot."
However the article makes the proviso that this only holds true if people are not tempted to change their e-readers when newer versions are brought out. When you look at how often people change their mobile phones - especially young people - that seems unlikely.