Back when I started flying as a kid, we did not have smartphones (or even cell phones), laptops, or various other electronic forms of entertainment. During long flights and layovers I entertained myself with coloring books, novels, and playing cards. My carry-on backpack was always heavy with books, books, and more books. It was the end of the world if I ran out of books to read on a trip! (I am a reading addict and I always have been)
Now, I always have my smartphone and my Nook with me on flights, but I always remember to bring one low tech novel just in case. I have been stuck in airports before, having forgotten my charger, and stuck with the newsstand book and magazine offerings. I have to admit, I love having a e-reader for traveling. As someone who would regularly pack 5 books of 400+ pages for a week long trip, the lightening of my load has been much appreciated. Yet, ever since that one trip with a forgotten charger, I will never forget to bring a backup book to read.