I hold an e-reader in my hand. Lighter than any paperback collection of Henrik Ibsen's plays, capable of holding more books than any piece of Ikea furniture. It lights up the display so I can read in the dark. If I want, I could dive into the ocean with such a device. And yet. There are two things I miss: context and skimming.
When you pick up a physical book and thumb through the pages to get the your place, you absorb a lot of context. Title, length -- perhaps you remember the last time you picked up this book and what you learned then.
When I pick up my e-reader, it snaps me right back at the exact page I was on before. It's work to go back through the book. You don't even see the title of the work you're reading. You just go straight to the content with little context.
Then there's skimming. It's easier to move through a physical book. You hold your spot with one finger and use your thumb through...hm where was that paragraph on...ah yes here it is. With e-readers, moving forward and backwards in a book is, imperceptibly yet crucially, a heavier action. And so I don't go back to reread that passage because it's harder to find in an ebook somehow. Sure you can bookmark things, but you need to remember to do that.
Perhaps there's a solution to these issues. Or perhaps our interactions with books will change. I'd love to see studies done on e-books vs physical ones. Does it change comprehension? Reading habits? Are there differences in how much and what people remember? Do people love reading from both equally? Do they live different aspects of reading? All questions we don't yet have answers to.