The Dark Tower I: The Gunslinger

He had gone often alone into the void places seeking the Imperishable Flame; for desire grew hot within him to bring into Being things of his own, and it seemed to him that Ilúvatar took no thought for the Void, and he was impatient of its emptiness. Yet he found not the Fire, for it is with Ilúvatar. But being alone he had begun to conceive though

The three main themes are thus The Delaying Elves that lingered in Middle-earth; Sauron’s growth to a new Dark Lord, master and god of Men; and Númenor-Atlantis. They are dealt with annalistically, and in two Tales or Accounts, The Rings of Power and the Downfall of Númenor. Both are the essential background to The Hobbit and its sequel.