Even the most faithful of big-screen adaptations can't capture every facet of their source material. Harry Potter and The Chamber of Secrets is no different. The question of whether the details left out of the movie undercut some aspects of the story is entirely subjective, but one can't deny that the second installment in the Harry Potter series sent it to new heights. Here are the biggest changes the movie made to the book.
Dinner With the Masons Was an All-Day Event
The Chamber of Secrets movie began with the Dursley family preparing for dinner with a couple who were potential investors in Uncle Vernon's company. It shared several elements with the book's version of events, including the Dursleys' rehearsed compliments and Harry's famous "I'll be in my room, making no noise and pretending I don't exist" line. But while this interaction happened right before the Masons arrived in the movie, the book had it happen at breakfast.
It's quite a minor change, but the narration of Harry's day after that breakfast gave an insight into what his life was like with the Dursleys. He was no longer forced to live in the cupboard under the stairs, but his adoptive family treated him just as they had before he'd left for Hogwarts. Magic was still very much a taboo subject, and Harry was sorely punished when he played a prank on Dudley involving nonsense magic words. His day spent slaving away in the book, coupled with the pitiful dinner Aunt Petunia gave him, made Dobby's request to stay home from Hogwarts seem all the more ridiculous, as the magical school was Harry's only respite from the Dursleys' abuse.
Knockturn Alley Hinted at the Malfoys' Secrets
Harry's first trip with Floo Powder ends as disastrously in the book as it does in the movie, with the only notable difference being the inclusion of Daniel Radcliffe's unique pronunciation of "Diagon Alley." However, his visit to Borgin and Burkes and his stint in Flourish and Blotts play out quite differently.
To begin with, Harry left Borgin and Burkes quite uneventfully in the movie, whereas in the book, both Lucius and Draco Malfoy visited the Dark artifacts shop before he could escape. The sinister father and son duo possessed some items that would have implicated them in Dark activity if discovered by the ministry and were visiting Borgin and Burkes to pawn them off. Harry waited till they concluded their business and managed to leave Borgin and Burkes without incident, but that wasn't the last he saw of them.
After reuniting with the Weasleys and Hermione Granger, Harry once again ran into Lucius and his son at Flourish and Blotts. Lucius sneered at the Weasley children's belongings, provoking the usually pleasant Arthur Weasley into attacking him. The two scuffled for a bit before finally being separated by Hagrid and the shop attendants. Their chaotic fight created the perfect cover for Lucius to slip Tom Riddle's diary into Ginny Weasley's cauldron alongside one of her textbooks.
Percy Weasley's Relationship with Penelope Clearwater
Percy Weasley, as the books presented him, was a much more annoying older brother than his movie counterpart. His role was severely minimized in the adaptation, and that did him many favors in regards to fan perception of his character, but it also left him somewhat bland and uninteresting. In the books, the other Weasley brothers noticed Percy was acting a bit oddly during their summer vacation and throughout the school year. They don't find out why until the end of the story, but his secrecy hid a romantic affair with the Ravenclaw prefect, Penelope Clearwater.
Penelope was never a main character in the books, but she's mentioned frequently enough that she almost becomes a household name among book fans. In the Chamber of Secrets book, Harry and Ron incorrectly assumed she was a Slytherin after they drank the Polyjuice Potion and asked for directions to their common room. Naturally, Penelope couldn't help there. She was also a victim during the basilisk attack that petrified Hermione. Both girls were discovered petrified together, but the movie had Hermione as the sole victim of that attack. In fact, apart from a greeting she and Percy exchanged with Nearly Headless Nick near the beginning of the movie, Penelope never appears at all.
Sir Nicholas' Deathday Party Provided Some Insight on Ghosts
In the Chamber of Secrets book, Harry rashly promised to be at Nearly Headless Nick's 500th Deathday party as a special guest. It was a predictably grim affair, as the ghosts had quite a different idea about what passed for entertainment and party refreshments, but at least he had Hermione and Ron for company. The music at the party was described as sounding like a "thousand nails on a chalkboard," and the food available was all rotten. Hermione mused that the food's state was intentional, as the rot would give it a stronger flavor so the ghosts could somewhat taste it.
Understandably, this party got cut from the movie because it was mostly inconsequential to the story's progression, but it would have provided some more depth to the ghosts of Harry Potter. The Deathday Party revealed that there were some customs, organizations and networks between the ghosts of the Wizarding World that movie-only fans never got to know. The Deathday Party's aftermath was where the real excitement began; right after they left, Harry heard the basilisk moving within Hogwarts' walls for the first time. What followed was the Heir of Slytherin's first attack on Mrs. Norris, Argus Filch's cat, and the declaration of their intent to purge Hogwarts of all Muggle-born students. In the movies, this scene followed a particularly dreary detention Harry spent answering Gilderoy Lockhart's fan mail.
Hermione Is Much More Powerful in the Chamber of Secrets Movie
Hermione Granger had a well-earned reputation for being the "brightest witch of her age," but she truly outdid herself in the Chamber of Secrets movie. She repeated a few of her most noteworthy feats from the books, including brewing the highly difficult Polyjuice Potion and deducing the species of Slytherin's monster, but her abilities went even further. After Lockhart was helpless to corral the pixies he'd foolishly unleashed on the class, Hermione stepped up and saved the day with a freezing charm. With one wave of her wand, she immobilized every pixie terrorizing the class, whereas, in the books, the same charm only affected three. She also deftly took care of the rogue Bludger that followed Harry throughout his first Quidditch match.
Hermione's competence, especially in the Chamber of Secrets movie, completely invalidated Salazar Slytherin's ideology. The Hogwarts founder felt that wizards descending from Muggles were inferior and left the monster for his descendant to carry out his perverse mission. This crusade made no sense; as Hagrid brilliantly put it, "they haven't invented a spell our Hermione can't do."