Most portraits of Ruth Dallas (born Ruth Mumford, 1919–2008) are taken from her left-hand side. Whether requested by the sitter or unconsciously adopted, this vantage point either obscures or minimises Dallas’s glass eye. Diana Morrow’s recently published A Writer’s Life, her captivating biography of Dallas—the first comprehensive study of “the Southern Woman of New Zealand letters”— gives it to us straight, painting a life as it was lived: brig…