J.R.R. Tolkien’s The Lord of the Rings was originally published in three volumes.
The volumes were The Fellowship of the Ring, The Two Towers, and The Return of the King. George Allen & Unwin published them separately between July 1954 and October 1955, although Tolkien conceived the work as one continuous story rather than a trilogy.
The three-volume format was influenced partly by postwar paper shortages and the practical cost of producing such a long book. Each volume was divided into two books, so the complete work contains six internal books plus appendices. This structure is why editions may describe the novel as six books, three volumes, or one story.
The phrase “trilogy” is common and useful, but Tolkien himself resisted treating the work as three independent novels. The volume titles also do not correspond perfectly to the story’s major plot divisions, especially in The Two Towers.