Original sentence: His most famous work was the epic three-volume novel The Lord of the Rings (1954-55), which, though a direct sequel to The Hobbit, was intended for a much older audience, drawing upon the immense back-story of Middle-earth that he had constructed and that eventually saw publication as The Silmarillion and in other posthumous volumes
Edited sentence: His most famous work was the richly inventive epic three-volume novel The Lord of the Rings (1954-55), which, though a direct sequel to The Hobbit, was intended for a much older audience, drawing upon the immense back-story of Middle-earth that he had constructed and that eventually saw publication as The Silmarillion and in other posthumous volumes