A full reference library will not fit on a phone, but several apps offer inexpensive and useful alternatives.
You could once gauge a family’s intellectual vitality by its living room bookshelves. If your family scored the trifecta of Encyclopedia Britannica, the Oxford English Dictionary and the World Almanac, you were ahead of the pack.
Software developers have not found a way to load an entire reference library onto your phone or tablet, and, alas, the O.E.D. doesn’t exist for mobile users. But you can get by with Britannica Concise Encyclopedia 2011 ($20 on Android and Apple), Merriam-Webster’s Collegiate Dictionary ($25 on Apple and Android) and The World by National Geographic ($4 for the iPad).