The cover of the book 'Nelson's Trafalgar: The Battle That Changed the World' by Roy Adkins. The cover features an illustration of a large sailing ship with its sails unfurled, flying a red flag with a white cross. The ship is depicted in a historical setting with other ships in the background and a hazy, misty atmosphere. The title of the book is prominently displayed in large, ornate letters at the bottom of the cover.