The fifth Harry Potter novel is the longest and darkest in the series, and the one in which the full weight of Voldemort's return begins to be felt. The Ministry of Magic, unwilling to accept that Voldemort has returned, launches a campaign to discredit both Harry and Dumbledore. A Ministry-appointed teacher, Dolores Umbridge, arrives at Hogwarts to enforce Ministry control over the school, and her particular brand of institutional cruelty proves in some ways more threatening than the Death Eaters themselves.
Isolated, disbelieved, and struggling with a violent connection to Voldemort's mind that he cannot control, Harry leads a group of students in forming Dumbledore's Army — a secret organisation dedicated to learning real defence magic in defiance of Umbridge's educational decrees. Meanwhile, a prophecy that connects Harry and Voldemort from the moment of Harry's birth moves closer to the centre of the narrative.
At over 750 pages, Order of the Phoenix is the series at its most emotionally demanding — a book about institutional failure, the loneliness of being right when the world is determined not to listen, and the cost of fighting a war that the powerful would rather pretend isn't happening. Rowling has acknowledged that Umbridge was inspired by a real person she once disliked intensely, describing them as someone with a pronounced taste for twee accessories.