Faramir

Faramir's character is completely changed. In the book, Faramir is one of the few characters who are not influenced by the Ring, who don't want to have it. He is the complete opposite of his brother, Boromir, and he doesn't take the Hobbits to Osgiliath.

Shelob

In the book, Shelob, a giant spider, already appears in part two of The Lord Of The Rings.

The Wargs

The fight with the Wargs doesn't exist in the book.

Aragorn and Arwen

Like in the first part, the story of Aragorn and Arwen normally doesn't appear in the book but only in the appendix. Moreover, Elrond doesn't ask Arwen to leave Middle-Earth in the book, he lets her decide whether she wants to stay with Aragorn or not.

Merry and Pippin

Merry and Pippin have a bigger role in the book. Tolkien tells more about their journey with the Uruk-Hai and about an arguement amongst the Uruk-Hai. Moreover, in the book, the Hobbits meet Treebeard in the wood (in the movie, Treebeard saves the Hobbits from an Orc). After they met the Ent, Treebeard takes the Hobbits to one of his caves. There they have a rest and the Hobbits taste from Treebeard liquid food, which makes them grow up. During this rest, Treebeard also tells the Hobbits about the Entwives.

The Ents

In the book the Ent thing takes much more time, and as the result, the Ents decide on their own to go to Isengard. In the movie, the Ents first didn't want to take part in the battle and it is Pippin who convinces Treebeard of going to Isengard.

Children

The story about the two children who are sent to Edoras by their mother to warn King Théoden is only an invention.

Théodred

The death of Théodred, Théoden's son, is not described in the book, but it is mentioned.

Eomer

In the book, Eomer returns to Edoras as soon as Théoden is healed. Moreover Eowyn stays in Edoras when the armies of Rohan ride to Helm's Deep. In the battle at Helm's Deep, Eomer plays a bigger part, while the Elves don't take part in it at all. In contrary to the movie, it is not Eomer who is brought with his army to Helm's Deep by Gandalf but Erkenbrand, Lord of Westfold.

Isengard

After the battle at Helm's Deep Gandalf, Aragorn and the others return to Isengard where they find Merry and Pippin, Saruman is locked in Isengard by Gandalf, Pippin uses a Palantír... But hopefully all that will be shown in the third movie.