Which book of the series has the most sophisticated plot structure?

i would prefer the first book, because it brings many new imagination, while all the next books are just following the first book, despite many greater things appear in the newer books. but i think Rowling put her base thought in her first book, Harry Potter and the Philosopher's Stone.

Keeping in mind that I haven't read the first and third books, no thanks to my sister, I would personally believe out of books 2, 4, 5, 6, and 7, I would say book 7. If you skip a single page in that book, you'll miss a whole section of plot. I know. I did it and ended up being very, very confused until I went back and reread it. Then it made much more sense.

My favourite book in the series was the final one.This is because of it being the final book of the series so i was excited when it came out and i remember the anticipation of reading it for the first time.I also think its the best written book of the series.This is because it has multiple storylines such as the search for horcruxes and hallows and epic action such as the battle of hogwarts.

Personally i loved the book 4 (Goblet of fire) and 7(deathly hallows). in the goblet of fire i like the tri-wizardy stuff and also the yule ball! all those new emotions for harry and everyone else were really exciting! book 7 tend to concentrate more on the characters, harry, ron and hermione as they haul in the forest, ministry of magic and so on. the fight with Voldemort was also nice, in the middle of the main hall and the older harry married with and older ginny that gets their children at the train is the top of the list! writing these messages i remember the feelings when i read those books a few years ago! :)

First and Second series every series had a lot of surprises but those two were excellent especially the first