The Hobbit was Tolkien’s first published Middle-earth book, released before The Lord of the Rings.
Published in 1937, the novel follows Bilbo Baggins on a journey with thirteen Dwarves and the wizard Gandalf. Its plot centers on the attempt to reclaim the Lonely Mountain and its treasure from Smaug. During the adventure, Bilbo finds the One Ring, although the object’s larger significance was developed more fully in Tolkien’s later work.
The Hobbit was originally written with a younger audience and a more playful narrative voice in mind. When Tolkien wrote The Lord of the Rings, the tone became darker and the mythology expanded considerably. The earlier book nevertheless supplied major characters, locations, and story elements for the sequel.
The Silmarillion was based on older mythology but appeared only after Tolkien’s death. The Two Towers is the second volume of The Lord of the Rings, not an earlier publication.