Harry Potter and the Chamber of Secrets is the story of the titular hero's second year attending Hogwarts School of Witchcraft and Wizardry. Amidst a series of mysterious attacks on the student body Harry must cope with the suspicions of his fellow students, the school's mysterious past, and the identity of the force behind the attacks. The story is an illustration of childhood friendship, the shadows of past sins, and the perils of false accusations in climates of paranoia.
Harry Potter and the Chamber of Secrets continues the examination of what makes a person who he or she is, which began in the first book. As well as maintaining that Harry's identity is shaped by his decisions rather than any aspect of his birth, Harry Potter and the Chamber of Secrets provides contrasting characters who try to conceal their true personalities: as Tammy Nezol puts it, Gilderoy Lockhart "lacks any real identity" because he is nothing more than a charming liar. Riddle also complicates Harry's struggle to understand himself by pointing out the similarities between the two: "both half-bloods, orphans raised by Muggles, probably the only two Parselmouths to come to Hogwarts since the great Slytherin."
Opposition to class, death and its impacts, experiencing adolescence, sacrifice, love, friendship, loyalty, prejudice, and racism are constant themes of the series. In Harry Potter and the Chamber of Secrets Harry's consideration and respect for others extends to the lowly, non-human Dobby and the ghost Nearly Headless Nick. According to Marguerite Krause, achievements in the novel depend more on ingenuity and hard work than on natural talents.
Edward Duffy, an associate professor at Marquette University, says that one of the central characters of Chamber of Secrets is a book, Tom Riddle's enchanted diary, which takes control of Ginny Weasley– just as Riddle planned. Duffy suggests that Rowling intended this as a warning against passively consuming information from sources that have their own agendas. Although Bronwyn Williams and Amy Zenger regard the diary as more like an instant messaging or chat room system, they agree about thedangers of relying too much on the written word, which can camouflage the author, and they highlight a comical example, Lockhart's self-promoting books.
Immorality and the portrayal of authority as negative are significant themes in the novel. Marguerite Krause states that there are few absolute moral rules in Harry Potter's world, for example Harry prefers to tell the truth, but lies whenever he considers it necessary– very like his enemy Draco Malfoy. At the end of Harry Potter and the Chamber of Secrets , Dumbledore retracts his promise to punish Harry, Ron, and Hermione if they break any more school rules– after Professor McGonagall estimates that they have broken over 100 – and lavishly rewards them for ending the threat from the Chamber of Secrets. Krause further states that authority figures and political institutions receive little respect from Rowling. William MacNeil of Griffith University, Queensland, Australia states that the Minister for Magic is presented as a mediocrity. In his article "Harry Potter and the Secular City", Ken Jacobson suggests that the Ministry as a whole is portrayed as a tangle of bureaucratic empires, saying that "Ministry officials busy themselves with minutiae (e.g. standardising cauldron thicknesses) and coin politically correct euphemisms like 'non-magical community' (for Muggles) and 'memory modification' (for magical brainwashing)."
This novel implies that it begins in 1992: the cake for Nearly-Headless Nick's 500th deathday party bears the words "Sir Nicholas De Mimsy Porpington died 31 October 1492".
Chamber of Secrets has many links with the sixth book of the series, Harry Potter and the Half-Blood Prince . In fact, Half-Blood Prince was the working title of Chamber of Secrets and Rowling says she originally intended to present some "crucial pieces of information" in the second book, but ultimately felt that "this information's proper home was book six". Some objects that play significant roles in Half-Blood Prince first appear in Chamber of Secrets : the Hand of Glory and the opal necklace that are on sale in Borgin and Burkes; a Vanishing Cabinet in Hogwarts that is damaged by Peeves the Poltergeist; and Tom Riddle's diary, which is later shown to be a Horcrux. Additionally, these two novels are the ones with the most focus on Harry's relationship with Ginny Weasley.