Is this movie based on a book?

Yes. The Lord of the Rings: The Fellowship of the Ring was based on the first book of The Lord of the Rings trilogy, written by the English academic and author J.R.R. Tolkien [1892-1973]. The other two books in the series (both movie and novel) are: (2) The Lord of the Rings: The Two Towers and (3) The Lord of the Rings: The Return of the King. The novels were adapted for the movie by New Zealand screenwriter Philippa Boyens, director Peter Jackson, and Jackson's wife, screenwriter Fran Walsh.