Which Tolkien book is the direct sequel to The Hobbit?

The direct sequel to The Hobbit is The Lord of the Rings. Tolkien began it after his publisher requested another Hobbit story, but the project grew into a much larger narrative about the One Ring and Sauron.

The Hobbit ends with Bilbo returning to the Shire after helping reclaim Erebor. The Lord of the Rings follows Bilbo decades later, when he gives the Ring to Frodo and retires to Rivendell. Frodo’s mission to destroy it drives the central plot.

The books differ sharply in scale and tone. The Hobbit is a compact children’s adventure centered on Bilbo, Thorin, and Smaug; The Lord of the Rings is an epic involving the fate of Middle-earth, multiple peoples, ancient history, and three linked volumes published from 1954 to 1955.

A common mix-up is The Silmarillion, which Tolkien had worked on before and after The Hobbit. It is chiefly a mythology and history of earlier ages, not the narrative sequel. Unfinished Tales is a posthumous collection of related material.