The book is a uniquely durable object, one that can be fully enjoyed without being damaged. A book doesn't require fuel, food, or service; it isn't very messy and rarely makes a noise. A book can be read over and over, then passed on to friends, or resold at a garage sale. A book will not crash or freeze and will still work when filled with sand. Even if it falls into the bath, it can be dried out and finished. Books require no special training to operate.