Which Tolkien work was originally written as a sequel to The Hobbit?

The Lord of the Rings was originally written as a sequel to The Hobbit.

After The Hobbit became successful, Tolkien’s publisher asked him for another book featuring hobbits. Tolkien began a new adventure, but the story gradually expanded into a much larger account of the One Ring, Sauron, and the history of Middle-earth.

The resulting work was published in three volumes between 1954 and 1955. Its narrative follows Frodo Baggins and a company of companions as they attempt to destroy the Ring in Mount Doom.

The Lord of the Rings is not simply a second children’s adventure like The Hobbit. Its tone, scale, invented history, and language became considerably more ambitious during Tolkien’s long period of composition.