Bakshi's most ambitious effort (and his most famous after his animated adaptation of the underground comic Fritz the Cat), the film was seen as a critical disappointment. It was produced by United Artists, but distributed to theaters by Warner Bros.
Much of the film used live-action footage which was then rotoscoped to produce an animated look. This saved production costs and arguably could have given the animated characters a more realistic look due to secondary animation that a traditionally animated film would not have included. Most critics seemed to believe that the sections of the film with rotoscoped animation were inferior in quality to "normal" animated films.
Additionally, the film ended somewhat abruptly after the battle of Helm's Deep, but before Sam, Frodo and Gollum traverse the Dead Marshes. The box-office disappointment of the film forced Bakshi to abandon his plans for a sequel.
In an attempt to "finish" Tolkien's story and make it more complete for audiences, Warner Bros. contracted with the Rankin-Bass animation studio to produce an animated TV special based on Tolkien's book. The first of these TV specials, The Hobbit, was a ratings success. This inspired Rankin-Bass to make a animated TV movie, an adaptation of The Return of the King, which finished the story and answered most of the questions raised by Bakshi's animated film.
However, several unresolved story developments between The Lord of the Rings and The Return of the King were left unresolved, especially the betrayal of Frodo by Gollum, and the attack of Shelob the monster spider-creature.