Umm… it doesn’t?
This is a particularly awkward “adaptation” to discuss, as both J.R.R. Tolkien and Peter Jackson have extensively developed their own versions of Middle Earth. Of course, there are a lot of Tolkien purists who are offended by Jackson’s re-imagining of Tolkien’s original.
My mother walked out of the first installment, The Hobbit: An Unexpected Journey, complaining that it was “just so silly, like a kids movie.” It was a good indication that it did actually resemble the children’s book that it was based on… in fact, all of the examples she complained about were threads I remembered from having read it, way back when I used to be young.
The second installment, The Hobbit: The Desolation of Smaug, had a lot more of “original Jackson” additions- many of which, I appreciated. I appreciate Tolkien’s world-building, but he specialized in mythology and mythology tends to rely heavily on “archetypes”… which can veer dangerously into stereotypes. So, I thought the film fleshed out some characters I hadn’t found very relate-able in the books. For instance, Gandalf. Even as children, my brother and I snickered endlessly about the questionable timing of his disappearance. This is how we summarized his exit speech many times through the years: “The most dangerous part of your journey stands before you. Even though virtually every time I’ve turned my back, you’ve nearly gotten yourself killed and I’ve only just managed to bail you out at the last moment, I think now’s a good time to leave you on your own. I’m sure you can handle it… based on how incredibly incompetent you’ve been so far!” In the movie, Jackson has imagined a scenario where Gandalf’s desertion was justified and in no way diminished his commitment to the friends he had to leave in danger’s way.
Jackson went hog-wild with additions and amendments in the third installment, The Hobbit: The Battle of Five Armies. The title of this movie does not lie. It felt like 95% BATTLE. I admit that I haven’t re-read The Hobbit recently, but I really don’t recall anything on this scale happening.
Of course, The Hobbit had been written as a stand-alone children’s book, but The Lord of the Rings trilogy expanded into a whole lot more. A lot of analogies have been drawn between it and World War II. It feels like Jackson took them and, working backwards, transformed The Hobbit into Middle Earth’s World War I. By that yardstick, it worked well.