Last month, during a family trip to Yellowstone National Park, my 9-year-old son asked how high the water from Old Faithful was spraying and why it was so hot and steamy. Armed with my smartphone and the Concise Encyclopedia Britannica application , I was able to touch, search, and tell: 160 feet high, and proximity to magma.

Did I need an e-book app on a mobile device to answer these questions for him? Probably not. A signpost or park ranger could have informed me, but the beauty of my solution was that I easily found the information at an altitude of 7,359 feet in a remote area of Wyoming. That's why, when people ask me why they should invest in e-books, I respond with "24/7 access anywhere and no shelf required."