Could someone with knowledge of the book say how much of this movie stuck strictly to the book and how much was extrapolation, percentage-wise, I guess? I hadn't read the book for a long time but don't remember half the exchanges in this movie from it.
There's a lot of little stuff, but this is most of the bigger stuff that was added and not in the book:
- The intro scene with Old Bilbo and Frodo
- The prologue depicting Smaug attacking Dale & Erebor
- The sequence with the three trolls was evolved into a full-on action sequence (it was much simpler in the book).
- The flashback sequence depicting the The Battle of Azalnulbizar (where Azog gets his hand cut off and Thorin gets his "Oakenshield" moniker).
- Literally every single scene involving Radaghast, he's not in the book at all. This includes his investigation of Dol Goldur, the scene with him and the spiders in his house, etc.
- Azog being a primary antagonist throughout the film(s). In the book he actually
did die at the Battle of Azanulbizar like Thorin suggests.
- The scenes involving Galadriel, as well as the White Council - not the in book.
- The Stone Giant encounter was made to be a big action set-piece in the film, when it's just one or two sentences in the book.
- The escape from Goblin Town was greatly expanded upon in the film to (another) big action set-piece.
- While the Wargs chasing the dwarves up the trees did happen in the book, Thorin's final 1v1 battle against Azog was also an invention of the film (because, again, Azog is long-dead at this point in the chronology of the books).
TLDR; Anytime there was a battle or action set-piece of any kind in the film, just assume it didn't happen in the book and was inserted by Jackson & Co. to liven up the screenplay. Because bare in mind that AUJ really only covers the first six or so chapters of The Hobbit - chapters in which no real "action" in a Hollywood sense occurs. After that (in the book) is when shit really starts to hit the fan.