Books are, as Stephen King put it, "a uniquely portable magic" – and the portable part is as important as the magic. A book can be taken away, kept hidden, your own private store of knowledge. (My son's personal diary has an ineffectual – but symbolically important – padlock.) The power of the words inside books is so great that it's long been custom for some words to be blanked out: such as swear words, as anyone encountering a "d—-d" in a 19th-Century novel will know; or words too dangerously powerful to be written down, like the name of God in some religious texts.
