Splitting Tolkien's book up into a trilogy of films like this, some have suggested a commercial motive. To which insiders have responded that those are people who “don't know Peter.” And they're right. For example, I have never met director Peter Jackson and I am suggesting that.
It's not just that Tolkien's first book was roughly a third of the length of 'Lord of the Rings'. That in itself is just an indicator of the way 'The Hobbit' was written in a very different tone. In a perhaps unusual move, Tolkien started off with a children's book then added a sequel for adults. I tend to think of it through Tove Jannson's illustrations; moody and myserious landscapes peopled by strange but cheery cartoon figures, at once otherly and homely.
Worse, take away that tone and you're left with the book's formal elements – which are uncannily similar to those of 'Lord of the Rings'. An unlikely hero joins a motley fellowship on a quest. It's quite often even the very same stops. If it's Thursday, this must be Rivendell. Oh, except instead of getting lost underground to orcs, this time it's goblins.
Plus of course it's all happening in the wrong order. I read... you read... everybody read 'The Hobbit' then progressed onto 'Lord of the Rings'. (I can distinctly remember seeing the fat one-volume edition in bookshops, thinking “one day I will be grown-up enough to read that.”) We read them in the order they were written.
Jackson's solution to that one is foreboding. (Tolkien buffs say a lot of this is stuff folded back from still-later works such as 'The Silmarillion.') Things in Middle Earth are taking a darker turn. Sinister figures loiter, Orcs are abroad, strange shadows fall. Pretty soon you won't be able to leave your windows open.
Particularly in the scene where Saruman shows up, it's hard not to be reminded of 'The Phantom Menace.' But then again, with all the problems that film filled itself, it's prequel ordering wasn't one of them. Plus Tolkien's compatriot CS Lewis wrote his Narnia chronicles out of chronology, starting off at quite possibly the darkest moment. The foreshadowing is probably quite a good idea. The problem is that this never seems a more innocent land, for the shadows to show up more starkly against. The Shire seems as provincially calm as ever. But that's precisely the way it was in 'Lord of the Rings'.
As you'd probably expect, things lurch from set-piece to set-piece like a video game. (Level 5 - Underground against Goblins. Level 6 – on a clifftop against Orcs.) Scenes can seem so overlong I'd claim the expanded director's cut has been released early, except that will tempt fate for the still-more-expanded director's cut that's doubtless to come. The warring rock giants epitomise one pole of the film. They look spectacular but add precisely nothing to the plot. They're not even overcome, really, they just do their thing and go away to leave us ready for the next thing.
But there is another pole of the film, in scenes which do seem more reminiscent of the book. (Or at least work the book into a contemporary film in a manageable way.) The Trolls are not CGI hordes but finite in number, and are (sort of) characterised. There's peril, but served with black humour. You're not quite sure whether to feel charmed or chilled. The scene where Bilbo first encounters Gollum is also effective. Notably both feature wordplay above swordplay, Bilbo battling Gollum by riddling.
But let's face it, we fans are probably making a category error to begin with. These films aren't made to be thought about. Whatever their claims to 'authenticity', they're there to go “oooh” to. A fan of the original trilogy will come away happy. The things you'd expect to happen happen. Except for the things you'd expect to happen in the two sequels. There's just enough Tolkien left in there to act as a kind of through line, to stop it becoming entirely lurching set-pieces like every other Jackson film.
It's like when Wily Coyote steps off the cliff edge, but doesn't fall so long as he keeps running. Things kind of get by on kinetic energy alone. Whether things will start to fall further in the two sequels... that remains to be seen.