You can turn on the electronics when you here the ping which indicates a certain altitude.
I was in San Antonio for Worldcon recently and in four flights I did not see any other reader than my own Kindle PW. I saw paper books and I saw iPads and computers used by people to watch video.
I did not bring any book this trip. The PW was perfect since I did not have to look for good lighting. On the other hand its light was noticeable so they told me to turn it off on each flight...