Well, I just finished reading it (been reading since 0200 this morning, stopping only briefly for lunch and about an hour of sleep) and it was pretty good.
Harry Potter returns to Hogwarts and finds that rather than a Quidditch tournament there will be a Triwizard Tournament instead. Nobody under 17 is allowed to enter but somebody enters his name and he gets chosen along with Cedric Diggory of Hufflepuff and two students from other wizard school.
Of course, Harry has more then just winning the tournament to think about. Why did somebody enter his name? Probably so he'd die (it's a very dangerous tournament). Plus he had a dream about Lord Voldemort plotting to kill him.
And on top of that, there's a reporter working for The Daily Prophet whom has been somehow learning all sorts of dirt about Harry and his friends and writing stories based on that which are primarily conjuncture and pure fabrication.
(Maybe I should write this next part small so people who haven't read the book don't have the entire thing ruined by me. If you haven't read the book, you shouldn't read the following paragraph)
In the end Lord Voldemort does return and tries to kill Harry but fails. However, he is not destroyed and with Cornelius Fudge refusing to believe that Lord Voldemort had returned it may be hard to prepare sufficiently. We'll have to wait for Book Five now.
As for the title change from Harry Potter and the Doomspell Tournament, I suspect that it was changed because of the anti-Harry Potter idiots. Naming the book "Doomspell" when it's already under fire for being "violent" and "occult" would be bad publicity. Clearly the Triwizard Tournament was orginially called a Doomspell Tournament. (The Goblet of Fire is what decides who's in the tournament, similar to the Sorting Hat.)
Harry Potter and the Sorcerer's Stone - Harry Potter and the Chamber of Secrets - Harry Potter and The Prisoner of Azkaban - Harry Potter and the Goblet of Fire - Harry Potter and the Order of the Phoenix
See: The Harry Potter Project