The first time I read Goblet of Fire I was probably 15, and it took me a year to finish. I didn't like reading a book of that size, I thought it was confusing, and it wasn't enjoyable at all. 
 Now being 25, I have a surprisingly new outlook on this book that I thought I would never have. It goes to show that even though this is a fantasy novel, this book felt like real life more than I thought it ever would. You have two best friends fighting, you have a boy (Ron) jealous seeing another girl being with another guy. We all know they have classes and exams, but the pressure to succeed is adamant even in this book. You have (view spoiler)[ a death towards the end that shook everyone to their core, yet it's subtle enough. Like a normal possible reaction, there really wasn't much reaction. (hide spoiler)] 
 An ending like this leads us to Angst Harry in book 5. 
 I've personally never heard anyone say Goblet of Fire was their favorite book, but I think it could definitely be the most revelational (I don't think that's a word but I'm going to use it anyway lol) book of them all according to IRL situations. 
 AND! The best news of it all, it only took me two weeks to read instead of a year lol!