This will be somewhat of a mixed review, because The Hobbit: An Unexpected Journey, the first of three rather long installments chronicling Bilbo Baggins’ adventure in Middle Earth, is somewhat of a mixed film. I will avoid spoilers for those who haven’t seen it yet and haven’t read the book, though I consider the start safe.
Director Peter Jackson chose to start with a prologue giving the background for this quest, the story of how Erebor, greatest city of the Dwarfs, fell to Smaug the dragon. This is the whole reason for the quest: thirteen dwarfs, the wizard Gandalf and little Bilbo Baggins the quiet, respectable, titular hobbit, go on an adventure to retake the city under the mountain from Smaug. It is not how Tolkien chose to begin the tale, but it worked well enough, though perhaps went on a little too long, and in general prologues seem to work better in film than in print.