Sounds like a silly question, doesn't it? Of course J.K. Rowling wrote Harry Potter and the Goblet of Fire. Her name is right there on the cover, she has publicly claimed it and accepted credit for it.
But I am not sure that the J.K. Rowling who wrote the four Harry Potter book was the same person as the J.K. Rowling who wrote books one, two, three and five.
The Rowling who wrote most of the Potter books is a master story teller, a clear and technically perfect writer, a person who cares about the details as much as she cares about the grand themes of her work.
The Rowling who wrote The Goblet of Fire, on the other hand, seems to me at least to have been a different person: a person in a rush, under pressure to take advantage of the building success of her first three books and publish book four as soon as she could.
The first three Harry Potter books were published in consecutive years -- 1997, 1998 and 1999 -- and each came in at between 200 and 300 pages. That's a remarkable creative pace but, considering the relatively brevity of the books and the simplicity of their plots, eminently reasonable. And these books are masterpieces, technically perfect in the details and creatively impressive in their overall achievement.
Goblet comes in at a whopping 636 pages but was still published only a year after The Prisoner of Azkaban. And, if you read it carefully, it is a sloppy sloppy book.
At a macro level, the plot is hyper-convoluted and nonsensical: once Voldemort manages to place Barty Crouch Jr. at Hogwarts with access to Harry, the entire Triwizard Tournament is rendered unnecessary. Crouch could simply port-key Harry to the graveyard on any one of the many occasions he had access to our young hero and, in the process, Crouch himself would not have had to be sacrificed.
Further, as I have pointed out elsewhere, there are significant problems with key points in this book, problems that should have been caught by Rowling in the writing:
1. Wormtail killed Cedric Diggory with his own wand and yet, when Harry's wand forces Voldemort's wand to regurgitate its most recent spells ("priori incantatem") in reverse order, Cedric emerges as if Voldemort's wand had killed him;
2. In the same "priori incantatem" scene, Harry's parents emerge from Voldemort's wand in the wrong order: it is made clear throughout the books that Voldemort murdered James Potter first, then was forced to murder Lily Potter in order to get to infant Harry, and so Lily should have emerged from Voldemort's wand first -- but James does; and
3. Rita Skeeter must have overheard the entire scene involving Harry, Dumbledore, Fudge, Snape, McGonagall, Sirius Black and the others in the Hospital Wing at the end of the book, including the confrontation between Fudge and Dumbledore -- once Hermione catches her at the very end of that scene, Skeeter could have been forced to write and publish the entire true story immediately so as to force Fudge to admit the truth. And render much of the plot of Book Five unnecessary.
Even so, it is in the details of the writing that the sloppiness becomes unhappily apparent.
I have chronicled in previous posts how skilled Rowling is at providing the reader background information from previous books in interesting ways while still moving the plot of the current book forward effectively. In Chapter 2 of the Goblet, however, she simply slaps it all into the story in long expository paragraphs. This continues in Chapter 3 and, despite a promising opening chapter, we are almost 40 pages in before the main plot even begins.
The book is also rife with the kind of small grammatical errors (for example, subject-verb disagreements, especially when she uses collective noun such as "group of students" but then uses the verb in its plural form "group of students were") that Rowling usually avoids, with run-on sentences (... and ... and ... and ... but) and with examples where she tells us something rather letting us discover it through action and dialogue.
For example, I opened the book at random and came up with this quote as an example of a run-on sentence:
'Lovely,' said Rita Skeeter, and in a second, her scarlet-taloned finger's had Harry's upper arm in a surprisingly strong grip, and she was steering him out of the room again and opening a nearby door.
It is possible, of course, that the failure is on the part of Rowling's editors -- perhaps all of her draft manuscripts arrived at the publisher's office replete with errors and the editors whipped them into shape.
Whoever it was, the fourth Harry Potter book fails to live up to the exceptional quality of writing of the other six. And I think it's because Book Four was a significant rush job. Even though it is a mammoth tome, neither Rowling nor her publishers saw fit to take the time necessary to make sure it was of the same quality as her earlier novels in their rush to publish it for their adoring and lucrative public.
