The Secret World of Og is a children's novel written by Pierre Berton and illustrated by his daughter Patsy. It was first published in 1961 by McClelland and Stewart. This Canadian classic has sold more than 200,000 copies in four editions. Of his forty-seven books, this was Berton’s personal favourite, partly because the characters were inspired by his own children. The Secret World of Og brought the author more fan mail than anything else he wrote – at least a dozen letters a week from children across Canada.