But sometimes the greatest and the mightiest are not expressed in US$ or the number of books sold.
So we would explore other spiritual books.
Like the Vedas.
Who wrote the Vedas?
I'm not a Hindu to competently answer the question.
How about a Hindu scholar?
The Vedas were first recited, from father to son, from Guru to disciple, and passed down orally. Eventually, as a written Sanskrit developed, they were recorded on leaves, but had to be re-scribed every hundred years or so. As for age, nobody knows. All we can say is 'Before recorded history."