I don't think so. About the only thing they changed was making Faramir successfully tempted by the prospect of taking the Ring.
I don't want to derail this thread any further, but you either haven't read the books or have severe problems with comprehensive reading. Let us take a closer look at the mischaracterizations of the main characters:
Gandalf
Far from the self-possessed and calculating wizard of the story, Gandalf becomes, at one point, crazed and panic-stricken. Both his hopes are diminished and his fears magnified in ways that are not in keeping with his role as a wizard. Gandalf's appointed mission was to contest, mostly indirectly, the Dark Lord and somehow prevent his conquest of Middle-earth. The Valar had sent him and the other Istari to act as their emissaries in Middle-earth for this purpose, but only Gandalf had not, in some way, been corrupted. In the screenplay, the discovery of the Ruling Ring, far from giving him hope of final victory, brings on a terror that temporarily overmasters him. He almost goes mad in his fear.
Later, in the third movie, Gandalf is overcome by the Witch-king. His staff is broken and he is saved from certain destruction by the horns of Rohan. In the book, however, Gandalf is set to challenge the Witch-king at the gates of Gondor before Rohan arrives. There, he is strong and lordly, prepared to confront the the Witch-king.
Gandalf is overall a much weaker character in the film than in the novel.
Elrond
One of the few remaining Noldorin lords in Middle-earth, Elrond, who is over 6,500 years old according to the book, has despaired of all hope and has lost confidence in Men. His attitude is one of capitulation, and his purpose therefore is simply to quit Middle-earth with as many of his people as possible. His opposition to the marriage between his daughter and Aragorn is taken to the extreme of deceit to prevent her from remaining in Middle-earth. It is only when he fears her outright death that he orders Narsil reforged and then delivers it to Aragorn in person. Throughout the screenplay, Elrond is deeply scornful of men. Isildur's fall was, to his mind, the fall of all Men, and he lacks any confidence in any Man or group of Men to save the honor of that kindred.
In a sense, Elrond himself has fallen. His fears dominate him until near the end of the screenplay, and his possessiveness of Arwen leads him to perpetrate a deception upon her. Knowing of her intent to forsake the immortal life and wed Aragorn, he deceives her by willfully withholding crucial information from her while convincing her to break fealty and abandon her betrothed. It took the intervention of the Valar to prevent the success of his deceit. In the end, he surrenders to the inevitable, but in this, too, his demeanor is one of capitulation.
Aragorn
A man presented by Tolkien as having a singular destiny for which he is prepared by Elrond and toward which he labours throughout his life, the movie version of Aragorn is, instead, a man of doubts turned inward. His love for Arwen becomes a weight around his neck, almost literally because of the jewel necklace she had given him. He is full of fears and self-doubt, and he is unwilling to embrace the destiny that had been pronounced over him at birth. He is named Estel, that is 'hope', by the Elves, but he is far from being the hope that they are expecting. The reluctant savior might play well in a movie, but it was not the character that Tolkien had written.
Thankfully, and somewhat surprisingly, Aragorn does stay true to Arwen even as she is in the process of forsaking Middle-earth and her oath to him. Aragorn had previously suggested to Arwen that she take advantage of her chance for a better life in the Undying Lands, and he later tells Galadriel that he would have her take the ship to Valinor, which is possibly a reflection of the doubt he suffers in the movie. In the story, Aragorn's destiny drives him as much as his love for Arwen, but in the movie, it seems that he would have Arwen without the kingship if he could.
Aragorn is portrayed as alone in the world without kith or kin, but in the story he has dozens of kindred, at least, among the Dúnedain, and the sons of Elrond were his especially close friends. (Note: Elladan and Elrohir, the sons of Elrond, do not appear in the movie.) In the screenplay, Aragorn takes the Paths of the Dead with only Legolas and Gimli, but in the story they are joined by thirty others including the sons of Elrond and one other named man, Halbarad.
When Aragorn challenges Sauron with the Palantír, far from wresting it to his will as he did in the story, he falls under Sauron's control and is overmastered by him. The jewel of Arwen is destroyed, which signifies the loss of her immortal life, and he is thrown back a defeated man. In the story, his use of the Palantír to reveal himself to Sauron is a brilliant stroke that accomplishes Aragorn's purpose. Sauron is terrified by the sight of the blade that had once defeated him, and his doubts and fears cause him to miscalculate his preparedness for war and launch his offensives prematurely. Unlike in the movies, Aragorn never despairs even when his doubts and fears are at their height.
Aragorn's nobility in the books is markedly reduced--he has no qualms about murdering an emissary in cold blood, for instance.
Frodo
Frodo, who resisted the power of the Ring much longer than most others could, was depicted as succumbing to it much more rapidly and was almost completely overmastered by the time he had reached Ithilien. Of his interrogation by Faramir in the story he could say, "I have told you no lies, and of the truth all I could," while in the screenplay, he told a bald and brazen lie about "the gangrel creature" that had been seen with him. Even under the strongest influence of the Ring, Frodo never lied in the story.
While it is true that Frodo is eventually so overcome by the power of the Ring that Sam must drive, and eventually carry, him on the Quest, the screenplay causes the loss of his will much more quickly and thoroughly. By the time they reach the top of The Stairs of Cirith Ungol, his wits are so completely scrambled that he does the unthinkable and forsakes Sam on the Quest. This is one of the most unacceptable plot changes to Tolkien fans because the friendship between Frodo and Sam is the solid road on which the Quest is driven. At no time does Frodo turn on Sam in this way in the book.
Sam
Tolkien regarded Sam to be the "chief hero" of the story, and his role was a key one in driving the Quest to completion. The screenplay, however, has Sam actually abandoning his master at a moment of highest danger--a moment where, in the book, came the most tender and poetic scene of the story in which Sméagol was very nearly reformed. The idea that Sam
could turn back from the Quest even if so ordered by Frodo is preposterous(in the movie version, Sam was seen walking down the stairs, crying until he accidentally slipped and fell to a cliff where he found the remains of the lembas Smeagol threw away. Angered, he looked up the stairs). There is no doubt that Sam's love for Frodo would have held him on the road even if he had to follow at a distance. He did not have to do so, however, because Frodo and Sam entered the tunnel of Shelob together in the book, and they fought the terror of Cirith Ungol together--until, of course, Frodo was overcome. Aside from this, Sam was depicted so faithfully that one wonders why the screenwriters felt the need to deviate so drastically at this crucial moment of the story.
Faramir
Faramir is a widely loved character in Tolkien's story. This is due to his wisdom and purity of heart that makes him a great leader and an excellent judge of difficult matters. Despite his love for his brother Boromir, he is his exact opposite. The Ring had no purchase on him, and he understood that it must not come near the White City. He and his men treated Frodo and Sam with courtesy and honor, and even Gollum, when he was captured, received only kindness.
A major departure in the movies is that, rather than assist Frodo and Sam on their quest, Faramir decides to send the Ring back to Minas Tirith, crossing the Anduin and forcing a dubious detour into the journey. However, while tempted by the Ring, he never attempts to claim it for himself. While Boromir tries to take it for personal use, Faramir intends that the Ring would be a gift for his father(although the temptation seems as harsh as it was on Boromir. In the movie version, Faramir, tempted by the Ring, intended to gain personal glory by taking the Ring to Minas Tirith). He also does not react with anger when Frodo refuses to give him the Ring.
The fact that Faramir and his men brutalized Gollum is another major change from his character in the book, and does not really match his character in the movie either. This is somewhat incongruous to the man that we see in the scenes with his brother. While Faramir's taking the Ring to Osgiliath may be explained by the desire of the screenwriters to have Faramir "grow" in his understanding, as well as create suspense, there is no explanation given for the brutality that he exhibits.
It is likely that these scenes were given to us for the development of Gollum in the film and that the filmmakers did not care how it reflected on Faramir.
Denethor
Instead of Tolkien's wise and mighty Lord of Men who had simply been overwhelmed by the lies of Sauron, Denethor is turned into an imbecile and madman. In him, nobility is reduced to premature and artificial senility. It might be argued that this was done so that there would be no ambivalence about Aragorn's takeover, but the degree and tone of these changes borders on the farcical. For example, to plunge from the Embrasure Denethor would have had to run up two levels and entirely across the city, all the while burning to death.
Arwen Evenstar
For some strange reason, the fate of Arwen is tied to the Ring as if its survival, and that of Sauron's, would precipitate her own death. Fears arose after the first movie that she was to be made into a warrior princess due to her replacement of the character Glorfindel, but then she fell in later movies into a weak and failing elf-maiden. While Tolkien's character was strong, bold, and independent in his story, the screenplay made her over into a frail and dependent child who was easily manipulated by a selfish father. Aragorn's love for her was used by Sauron to strike a blow against him and prevent him from mastering the Palantir to his own will.