Films will always be different to the books they're based on. How different is The Hobbit (the book) from the films An Unexpected Journey and The Desolation of Smaug?
1. Dwarf Fashion Sense
In the book all of the Dwarves are described as wearing hooded cloaks of varying colours. Balin wore red and Thorin wore blue. Thankfully Peter Jackson dispensed with the garden gnome look for something more varied.
2. Thorin Oakenshield's Age
You wouldn't know it from the film but Thorin is the oldest of the Dwarves, even older than grey bearded old Balin.
3. Thorin's Dignity
Unlike in the film Thorin does not arrive at Bilbo's house fashionably late. He actually finds himself under a pile of fallen Dwarves when Bilbo opens the door of his house like a pop gun.
4. Speaking Dwarvish in Public
This is a big no-no. The Dwarves were notoriously secretive towards non-Dwarves, even those they considered friends. Not only do Dwarfs point blank refuse to teach other races their language but they would not even speak it in front of non-Dwarves except in extremis. Even the names are the Dwarves are made for the benefit of outsiders. No one knows their real Dwarvish names.
5. Taking Back Erebor
Actually reclaiming their ancestral homeland was only the secondary objective of their quest. Being Dwarves what they really wanted was the gold (hence the need for a burglar).
6. The Dwarves Washed the Dishes
No Bilbo did. And he was not happy about it.
7. Going on an Adventure
Despite point number 7 Bilbo did not turn down the offer of work as a burglar. He didn't accept it either. Gandalf woke him up and rushed him out the door before he could think on the matter.
8. The Death of Thror
Thorin's grandfather was not killed at the Battle of Azanulbizar as in the film. He was however killed by Azog in Moria which sparked the War of Dwarves and Orcs which culminated in the Battle of Azanulbizar.
9. The Non-Death of Azog
Azog did not survive the Battle of Azanulbizar as he did in the film (albeit minus a hand). He was killed by Dain Ironfoot (to be played by Billy Connolly in the final part of The Hobbit trilogy).
10. Glowing Swords
Bilbo's Elvish sword Sting glows when orcs are near. Why don't the Elvish swords of Gandalf and Thorin, found in the same Troll cave, glow as well? Ask Peter Jackson.
11. Dol Guldur, The Old Fortress
In the film Gandalf did not know that Dol Guldur was occupied by the Necromancer. In the book he did. He'd been there himself and met Thorin's father who'd gone mad in the dungeons of the Necromancer.
12. The Lonely Mountain
At the end of An Unexpected Journey our heroes get their first glimpse of the Lonely Mountain despite being hundreds of miles away. In fact the first sighting of the mountain was just after the company left Thranduil's realm.
13. Mirkwood Madness
Mirkwood is only dangerous if you leave the path. According to Peter Jackson the Dwarves make this error because of a magical spell that causes temporary insanity. The real reason is much less glamorous. The Dwarves ran out of food and tried to find some off the path.
14. Morgul Madness
You've heard of a Morgul Blade? Well apparently now you can get a Morgul Arrow and what's more it's standard issue for orc archers. Kili gets hit by one as it was the only way he could get Tauriel to massage his leg. Complete invention.
15. Family Breakup
Thanks to the above Kili and Fili don't join the other Dwarves in going to the Lonely Mountain. Bofur also stays behind because he woke up to late and literally missed the boat. In the book all the Dwarves made it to the mountain.
16. The Arkenstone
The film implies that Bilbo was brought along solely to recover the Arkenstone. While Thorin was indeed rather obsessed with this, Bilbo was still tasked with recovering us much of the treasure as possible (if not all of it).
17. The Black Arrow
In the book Smaug is killed by Bard using his bow and "Black Arrow". Presumably because it would look absurd on film for a gigantic dragon to be killed by a normal sized arrow, the Black Arrow has been upgraded to an iron bolt to be fired from a ballista.
18. Smaug's Wound
Smaug has a weak point on his left breast. The film claims this was due to a hit from a black arrow caused by Bard's ancestor. The book puts it down not to a wound but simply to the lack of gold and gems embedding themselves in his body.
19. Smaug's Rage
Smaug ends the film flying off to Laketown in a rage after being cofounded by Thorin and the Dwarves. Actually Bilbo managed to annoy the dragon all by himself merely by using his wits and stealing a cup.
20. Missing Presumed Dead?
Thorin's father Thrain is missing. In the book he's dead. Is he going to appear in part three?