The book on which the three films are based is conventionally, and incorrectly, referred to as a trilogy ...a term that describes three books that are related but each a complete work in itself--able to stand independently of the others. Lord of the Rings is actually a single novel divided into three parts by the publisher for reasons of convenience. Critics who call The Two Towers a sequel are mistaken. It is part two of a three part work, and is best judged as such. As such, and anticipating a similar quality level in the as-yet-unseen third intalment, it is excellent work. Jackson's emendations were by and large more respectful of the novel than anyone has a right to expect, given the film industry's historically rocky relationship to literature, especially great literature.