HOW KIND OF Peter Jackson: for the price of one movie, he gave us two. One of these movies is about a heroic warrior prince fighting for his lost homeland, and some political intrigue with elves and wizards; the other, much shorter, movie concerns a hobbit.

Written by J.R.R. Tolkien as a book for children, The Hobbit is widely regarded as a prelude to the darker and more complex Lord of the Rings trilogy. The One Ring that is the focus of The Lord of the Rings, and which threatens to destroy Tolkien’s world of Middle Earth, is first discovered in The Hobbit by the protagonist Bilbo Baggins. The true nature of the ring is never revealed in The Hobbit — it is depicted simply as a magic ring that conveniently endows Bilbo with the ability to become invisible.

In contrast to The Lord of the Rings, where nothing less than the fate of the world hangs in the balance, the central quest of The Hobbit is almost quaintly small-scale — to defeat the dragon Smaug and regain the stolen treasure that is the birthright of the dwarf prince Thorin Oakenshield. The book’s protagonist is correspondingly small in scale: Bilbo is a hobbit, which in Tolkien’s world is a humanlike creature about the size of a child, hesitant to enter into any conflict or unfamiliar circumstance, and extremely fond of food. When Bilbo joins the dwarves in a quest to regain their treasure, it is largely because he is tricked into it by the wizard Gandalf the Grey, who has decided that Bilbo has more mettle in him than the ordinary hobbit. The book continues in this sort of charming, low-stakes vein almost until the end: the sense one has of the dwarves’ quest is that of a tiny thread amid the vastness of Tolkien’s universe. For the purposes of the story, this quest mainly exists to force Bilbo out into the world to discover depths in himself that he never knew he possessed.

The moment news came that The Hobbit was going to be stretched into an immense movie trilogy, the outcome should have been obvious, but I still allowed myself to hope. After all, somehow Pride and Prejudice made an excellent six-part TV series for the BBC, ensuring that all future film adaptations would seem rushed in comparison. With a lavish attention to the details of Tolkien’s world, I reasoned, perhaps three movies would afford the filmmakers an opportunity to do justice to the richness of Middle Earth. But in that reasoning I was optimistically overlooking evidence from the Lord of the Rings movies that when it comes to the director’s take on Tolkien’s world, a better title for all the above movies would be The Battle Fantasies of Peter Jackson. Battles that are mere paragraphs or chapters in The Lord of the Rings books are the centerpieces of Jackson’s films. For this director, Tolkien’s stories often seem little more than backdrops for cinematic experiments with CGI and catapults (or CGI catapults).

But that isn’t fair, some would argue. The saga of Thorin’s family background and Gandalf’s concerns about a rising evil do exist, in the notes where Tolkien recorded an enormous amount of information that never made it into The Hobbit or the subsequent trilogy. (Some of these apocryphal notes are included as appendices to The Lord of the Rings; others have since been collected in numerous vo...