Time has a story entitled: “Do E-Books Make It Harder to Remember What You Just Read?” that ends up leaning more toward the problem occurring with learning and eTextbooks, than with fiction reading on  E Ink Readers such as Kindle, Kobo or Nook.
I know from personal experience that E Ink reading did require some adjustment and orientation, but that was accomplished by me either taking the time to remember where I left off in the narrative (as opposed to looking for dog-eared pages, or other mode of physical measurement) and it encouraged me to set the eReader aside when I became too tired to remember where I was in the story.
All of it, is just part of the learning curve on the way into the eBook Revolution.