What is the name of J.R.R. Tolkien’s only completed Middle-earth novel published after The Hobbit?

J.R.R. Tolkien’s only completed Middle-earth novel published after The Hobbit is The Lord of the Rings.

Tolkien wrote The Lord of the Rings as a sequel to The Hobbit, but the project grew into a much larger and more serious work. It was published in three volumes—The Fellowship of the Ring, The Two Towers, and The Return of the King—between 1954 and 1955.

Although commonly called a trilogy, Tolkien regarded it as one novel divided into volumes because of its length and publishing constraints. The story follows the quest to destroy the One Ring and the wider conflict against Sauron.

The Silmarillion is another major Middle-earth book, but it is a posthumous editorial compilation rather than a completed novel published by Tolkien during his lifetime. Unfinished Tales and The Children of Húrin were also assembled or edited from Tolkien’s later writings.