“Words matter,” begins a publisher’s note appended to the copyright page of the latest editions of Roald Dahl’s iconic children’s books. Yes, they do. Dahl knew that better than anyone as he was one of the world’s greatest wordsmiths ever and took extraordinary care over every word he wrote. “You must be a perfectionist,” he said. “That means you must never be satisfied with what you have written until you have rewritten it again and again, making it as good as you possibly can.” But editors at Puffin, who now publish the late author’s books, decided they could improve on...