Very disappointing, especially for fans of the original

Rating: 3/10 (10 January 2014)

For people who have not read the book: 6 stars (OK, not great) For those who have read the book: 1 star (awful)
This movie was, to put it bluntly, meh.
First of all, I'm a die-hard Tolkien fan. I've read the Lord of the Rings series several times, and the Hobbit several more. I've read the Silmarillion, and even some of Tolkien's non-canonical works that were published posthumously by his son. To me, the Lord of the Rings movie series were almost perfect. Although they deviated from the plot in (mostly) minor ways, they portrayed the spirit of the books exceedingly well, and had amazing special effects and great actors/actresses.
The Hobbit: An Unexpected Journey was very good as well. It annoyed me a bit that they added the white orc and some other (seemingly) minor details, but it's Hollywood and they have the right to take certain liberties.
However, the Desolation of Smaug was ridiculous. It's pretty good as a movie, and I'm sure people who haven't read the books will enjoy it. However, if you know anything at all about the original story, you'll know that this is not it. The vast majority of the movie had absolutely nothing to do with the book. At the very beginning, the company arrives at Beorn's house. Beorn was one of my favorite characters in the book, but I couldn't help hating him in the movie. Later, the company escapes from the elves in barrels. There was no fight in the book, but the movie takes a solid ten minutes or more as we watch Bombur bounce along the shore, killing orcs every time he lands, while Legolas, a female elf (I forget her name) and the rest of the dwarfs fight against orcs sent to kill the dwarfs. Arriving in Lake Town, the dwarfs are once again attacked by orcs who invade the city while Kili almost dies from a poisoned arrow wound. Eventually Thorin and company leave for the mountain, leaving four of the dwarfs behind in Lake Town. After Bilbo sneaks into the mountain, the dwarfs actually fight Smaug.
None of these things happened in the book, though they are a large majority of the movie. Many of the fights seem completely over the top and unrealistic, even for a fantasy movie. There is a strange romance going on with Kili and the elf lady, which seems to be just thrown in, in hopes of attracting more of the sentimental audience. The fight with Smaug never happened, and even the scene with the spiders was completely different from the book. They also left out several important parts from the book, and very little of the original plot remains.
All in all, it seemed like the movie was just haphazardly thrown together with no thought for the story or for any sort of continuity. It's as if the producers just thought "yes, we're making a movie about the Hobbit, but Tolkien didn't know what he was doing, we can write something SOOO much BETTER!!!" and then failed miserably. It would have been a ten-star movie if they had simply stuck to the plot of the book. It also appears as if they really just wanted to show off their fantastic special effects in whatever way possible, so they added a ton of random unnecessary fights, including a massive battle between Smaug and the dwarfs. Or rather, between Smaug and 9 of the dwarfs, since they left four behind. This is completely out of character, and it makes Thorin out to be a much more selfish and uncaring person than he is. The only redeeming factor in this movie is Bilbo. Martin Freeman does an excellent job portraying this little Hobbit who is slowly finding his courage.
The only explanation I can think of is that the directors and producers wanted to make this movie a prequel to The Lord of the Rings. The Hobbit is not a prequel, it is an almost completely unrelated story. But I'm sure they thought they could make more money from a prequel for fans who haven't read the books and wouldn't know any better.
Do yourself a favor: read the book. This movie is OK if you don't compare it to the book, but it's not great. And when compared to Tolkien's work, The Hobbit: The Desolation of Smaug looks like a mockery. I hope they do better on the next one, but I am quickly losing my faith in this trilogy. As an avid Tolkien fan, I was severely disappointed.