The 7 books in publication order
Publication order IS the chronological order of the main story. J.K. Rowling wrote the saga in that order, designed her mystery for that sequence, placed her clues in that chain. This is the order to respect.
1. Harry Potter and the Philosopher's Stone (1997)
You discover that Harry, an orphan mistreated by the Dursleys, is a famous wizard. He enters Hogwarts, befriends Ron and Hermione, discovers Quidditch, and faces the Philosopher's Stone coveted by a mysterious teacher. Youngest tone of the saga.
2. Harry Potter and the Chamber of Secrets (1998)
Second year at Hogwarts. Mystery: who is petrifying students? A diary speaks, a Basilisk roams, Hermione is struck. Harry discovers Parseltongue, and the first Horcrux is quietly introduced (you'll understand later).
3. Harry Potter and the Prisoner of Azkaban (1999)
Sirius Black has escaped. Dementors at Hogwarts. Lupin teaches defensive spells. Harry learns who his parents really were, and that he has a godfather. Narrative turning point — the saga grows darker.
4. Harry Potter and the Goblet of Fire (2000)
The Triwizard Tournament comes to Hogwarts. Harry is mysteriously entered. He faces a dragon, Merpeople, a maze. By the end, Cedric Diggory is killed and Voldemort returns physically. The saga tips into tragedy.
5. Harry Potter and the Order of the Phoenix (2003)
A dark year. The Ministry denies Voldemort's return. Dolores Umbridge terrorises Hogwarts. Harry founds Dumbledore's Army, studies Occlumency, and loses Sirius at the Ministry. The longest book (over 850 pages).
6. Harry Potter and the Half-Blood Prince (2005)
Harry explores Voldemort's past via memories Dumbledore has collected in the Pensieve. Horcruxes are introduced. Snape becomes Defence teacher. Dumbledore dies on the Astronomy Tower. The most cerebral of all books.
7. Harry Potter and the Deathly Hallows (2007)
Harry, Ron and Hermione leave Hogwarts to hunt Horcruxes. Camping, tension, Ministry infiltration, Gringotts escape on dragonback, Battle of Hogwarts, ultimate Snape reveal. Masterful finale. One epilogue chapter set 19 years later.