An old joke in linguistics runs: What is the difference between a language and a dialect? (Pause for dramatic effect.) A language is a dialect with its own army.
David Moser, author of A Billion Voices: China’s Search for a Common Language, has heard the joke; he even addresses it. But in the midst of a compelling discussion of a generally overlooked subject — the centrality of establishing a common tongue and a shared written language for all of China — it still mocks from the margins.