The book came out in 1970, but I never heard of it until today, when I read about the new film of the book. The title is what threw me. Shouldn't there be a comma after "there," since the question− "Are you there?" − is being addressed directly to God? Otherwise, and especially if you hear the name of the book or film said aloud, it might well sound like "Are you their god?"
It's not as if whoever decided on the title of the book was comma-averse. Otherwise, the full title would read:
"Are you there God? It's me Margaret."
But in that case we'd have another problem, because in some English-speaking countries, "my" is often pronounced as "me."