Grade: C

It’s probable that fans of the “Lord of the Rings” films will be so happy to return to Middle Earth with director Peter Jackson as their tour guide that initially they’ll greet “The Hobbit: An Unexpected Journey,” the first of three pictures loosely adapted from J.R.R. Tolkien’s slim book, with unmodified rapture. But one suspects that after the passage of time dulls the initial spasm of preordained enthusiasm, they’ll come to the same conclusion about it that devotees of “Star Wars” eventually did about the first prequel to another beloved trilogy, “The Phantom Menace.” That is, it’s just not very good.

The thin plot is presented as an autobiographical flashback told by hobbit Bilbo Baggins (Ian Holm), whose nephew Frodo (Elijah Wood) was the hero of the “Rings” films. (A pleasant but short prologue reintroduces the duo, and it’s nice to make their all-too-short reacquaintance.) In the recollection that follows, young Bilbo (Matthew Freeman) is enlisted by the wizard Gandalf (Ian McKellen) to join a baker’s dozen of dwarfs in a journey to the Lonely Mountain, where they hope to recover the kingdom of Erebor taken from their people years before by the ravenous dragon Smaug. He’s almost as reluctant to volunteer for the adventure as the stern, determined leader of the dwarfs, Thorin (Richard Armitage), is to have him tag along—but Gandalf insists.

So off they go, leading to a series of hostile encounters with trolls, goblins and a horde of gruesome orcs whose snarling leader is intent on exterminating Thorin. Along the way the merry band will also meet some faces familiar from the earlier trilogy—elf king Elrond (Hugo Weaving) and his ethereal, prophetic queen Galadriel (Cate Blanchett) and wizard Saruman (Christopher Lee), as well as Andy Serkis’ performance-capture Gollum, with whom Baggins has an extended scene toward the close that essentially sets the stage for the “Rings” scenario. There are also new characters introduced, most notably a third wizard, reclusive forest-dweller Radagast (Sylvester McCoy), who brings Gandalf an alarming report of a mysterious figure called the Necromancer who can actually raise the dead. That whole section of the picture, however, feels like a digression clumsily melded into the main plot.

All of this basically amounts to little more than a series of chases, captures and escapes in which Gandalf almost always saves the day at the last moment with some feat of sorcery. The major exceptions are the opening reel, which shows Smaug’s assault on Erebor in full throttle as well as a supposedly riotous dinner scene with the dwarfs around Bilbo’s table; the troupe’s stay in the mountainside elfin kingdom of Rivendell, which offers a breather from all the mayhem; and that sequence featuring Bilbo and Gollum, a long dialogue scene that would certainly work better if Serkis’ side of the conversation, in which the actor’s voice is artificially distorted, weren’t just about as unintelligible as the masked villain Baine’s lines were in “The Dark Knight Rises.” The last big action confrontation finishes up, cheekily enough, with a literal cliff-hanger, though there’s a postscript that points to the next leg of the quest.

What this scenario—cobbled together from Tolkien’s book, his addenda to “The Lord of the Rings” and the imagination of Jackson and co-writers Fran Walsh, Philippa Boyens and Guillermo del Toro (who was once scheduled to direct)—offers in spades in the opportunity for lavish CGI effects, which often take over so completely that they virtually turn whole sections of the film into pure animation (sometimes, as in the case of a fight between two rock monsters that look like they wandered in from “The Neverending Story,” having no apparent connection with the basic plot at all. The result is reminiscent of Ray Harryhausen fondly-remembered stop-motion pictures, but while “The Hobbit” is twice as long as any of Harryhausen’s Dynamation fantasies, it isn’t half as much fun as any of them.

That’s largely because unlike in “Lord of the Rings,” the effects pretty much overwhelm everything else. Apart from Freeman’s amiable Baggins, who sometimes reminds one pleasantly of Harpo Marx, there are really no characters in this picture that one can really care about. It’s fun to see McKellen, for example, arch his eyebrow or curl his lip, but that’s about all he’s given to do, while McCoy makes little impression and in their cameos Weaving, Blanchett and Lee barely register. And frankly the dwarfs don’t pick up the slack. A few of them are physically distinctive, but much less so in personality terms; and as their leader Armitage is simply a bore, a bland journeyman actor trying to strike a heroic pose and never managing to do so. That blunts the intended emotional impact of Thorin’s last-minute recognition of Bilbo’s courage.

Of course, the movie is technically a marvel, but goofy trolls, snarling orcs and a lip-smacking goblin king with a pronounced goiter (and even Gollum), no matter how splendidly rendered in the usual plastic manner, can’t make up for the absence of human-like figures you can identify with. Still, one has to admire the craftsmanship of Jackson and his crew, even if the much-ballyhooed high-frame-rate 3D process in which the picture was shot proves a mixed blessing, increasing clarity in action scenes but otherwise giving the images elsewhere an even more artificial look.

Like “The Phantom Menace,” “The Hobbit” has a built-in audience of fans who will rush to return to a cherished fantasy world, and feel obliged to say how wonderful the experience was. After a few months of reflection, however, one suspects that most of them will admit the unhappy truth that this return visit to Middle Earth is a bloated letdown.