There may be something to the idea that e-books make it harder to remember what you just read.  It's subtle, but I think it's there.
http://healthland.time.com/2012/03/14/do-e-books-impair-memory/
   http://healthland.time.com/2012/03/14/do-e-books-impair-memory/

Comments
Of course, I still haven't read the article. Or maybe I did and I forgot.