<p>'Suddenly it hits you: you're not twenty; you're not young any more . . . and in the meantime, while you were thinking about something else, the world has changed.'<br>Birthday begins with a fiftieth birthday. It comes and goes without fanfare, but just a few months later, an apparently banal comment that reveals a gap in the author's knowledge of the world prompts him to sit down in a café and write. As he sifts through anecdotes and weaves m...