The series was originally published in English by Bloomsbury in the United Kingdom and Scholastic Press in the United States. A series of many genres, including fantasy, drama, coming-of-age fiction, and the British school story (which includes elements of mystery, thriller, adventure, horror, and romance), the world of Harry Potter explores numerous themes and includes many cultural meanings and references. Major themes in the series include prejudice, corruption, madness, love, and death.

Harry becomes a student at Hogwarts and is sorted into Gryffindor House. He gains the friendship of Ron Weasley, a member of a large but poor wizarding family, and Hermione Granger, a witch of non-magical, or Muggle, parentage. The trio develop an enmity with the rich pure-blood student Draco Malfoy. Harry encounters the school's headmaster, Albus Dumbledore; the potions professor, Severus Snape, who displays a dislike for him; and the Defence Against the Dark Arts teacher, Quirinus Quirrell. Quirrell turns out to be allied with Voldemort, who is still alive as a weak spirit. The first book concludes with Harry's confrontation with Voldemort, who, in his quest to regain a body, yearns to possess the Philosopher's Stone, a substance that bestows everlasting life.

In the sixth book, Harry Potter and the Half-Blood Prince, Snape teaches Defence Against the Dark Arts while Horace Slughorn becomes the Potions master. Harry finds an old textbook with annotations by the Half-Blood Prince, due to which he achieves success in Potions class. Harry also takes private sessions with Dumbledore, viewing memories about the early life of Voldemort in a device called a Pensieve. Harry learns from a drunken Slughorn that he used to teach Tom Riddle, and that Voldemort divided his soul into pieces, creating a series of Horcruxes. Harry and Dumbledore travel to a distant lake to destroy a Horcrux; they succeed, but Dumbledore weakens. On their return, they find Draco Malfoy and Death Eaters attacking the school. The book ends with the killing of Dumbledore by Professor Snape, the titular Half-Blood Prince.