All proceeds apace with the Harry Potter Project, my determined effort to (finally) read the entire seven-book series. Goblet of Fire won the Hugo Award for Best Novel in 2001, and, yes, it's pretty good.
The first three books were combinations of white meat (whimsy and humor) and dark meat (danger and death). In Goblet of Fire, the dark-to-white ratio is turned way up; the book (for example) starts with the nasty murder of an innocent Muggle, committed by Lord Voldemort and his minions. There are creepy episodes of mortal danger throughout, and, unlike the previous three books, the climax is pretty much a victory for the forces of evil.
Also, for the fourth year running, it appears the Defense Against the Dark Arts teacher won't be back next year. Why would anyone take that job?
The more innocent fun, such as it is, lies in adolescent boy-girl stuff. Hogwarts is hosting the Triwizard Tournament, inviting two other schools of wizardry to compete; this brings in some new characters, some of whom offer romantic interest to the Hogwarts students. A celebratory Yule Ball turns disastrous for Harry and his friends, not by Voldemort's efforts, but by their own mundane teenage jealousies, misunderstandings, rivalries, and unintentional slights. As most post-teenagers reading the book will admit: been there, done that.
Some subplots in the book approach social commentary: our heroes are bedeviled by Rita Skeeter, a tabloid journalist who twists her news stories into innuendo-filled attacks, "evidence" obligingly provided by anonymous sources. Hermione takes on a do-gooding cause when she discovers that Hogwarts' army of house-elves are unpaid; she sets up a society to release them from their exploitation, but runs into an inconvenient fact: the elves themselves are basically satisfied with their lot in life. And the fight against Voldemort is greatly complicated by the unwillingness of bureaucrats in the Ministry of Magic to take the threat seriously.