Williams also wrote non-fiction books: The Middle Ages, Knights of the Crusades, The Spanish Armada, and Joan of Arc, as well as his young adult Landmark book on World War II, The Battle for the North Atlantic.
Williams schrieb auch Sachbücher: The Middle Ages, Knights of the Crusades, The Spanish Armada und Joan of Arc, sowie sein Hauptwerk über den Zweiten Weltkrieg für Jugendliche, The Battle for the North Atlantic.