C.S.Lewis’ second venture into Narnia, Prince Caspian, is sandwiched between two popular favorites, The Lion, the Witch and the Wardrobe and The Voyage of the Dawn Treader. Coming between the formidable creative and allegorical achievement of the former and the bracing, poetic odyssey of the latter, Prince Caspian is perhaps something of an awkward middle child.

Thematically, the book follows up the Narnian passion-and-redemption story with a vision of post-Enlightenment skepticism, in which the very existence of the omnipotent Lion Aslan and of High King Peter and his siblings has been largely forgotten, suppressed or dismissed as a fairy tale.

Yet Lewis’ tale is slow in starting, with two rather static opening chapters in Narnia before the first Narnian shows up, followed by four chapters of back story told in flashback, followed by a long trek through the Narnian countryside. For filmmakers in post-Peter Jackson Lord of the Rings Hollywood, Caspian is something of a challenge, a hurdle between more cinema-ready adventures.

For better and for worse — and it’s quite a bit of both — the big-screen Prince Caspian takes far more creative license than its predecessor. There is definitely an upside: Caspian is a better-made film. In some ways, it manages to improve on Lewis’ plot without violating its spirit.

Returning director Andrew Adamson and his co-writers make choices that, in terms of plot and spectacle, are generally defensible and often even helpful. An early conflation of events gets the action going faster, opening with Caspian (Ben Barnes) fleeing from his murderous uncle Miraz (Sergio Castellitto), and drawing Peter, Susan, Edmund and Lucy (William Moseley, Anna Popplewell, Skandar Keynes and Georgie Henley) into Narnia much earlier in the story.

Two of the film’s most successful sequences — one at Miraz’s castle and the other in the depths of Aslan’s How — are also two of its boldest departures, though both have roots in the book. Fans may make much of the sparks that fly between Peter and Caspian over which of them is in charge — as well as the quite different sort of sparks between Caspian and Susan — though the spirit of Lewis’ story could survive either of these revisionistic touches.

The more serious problem is that, while the essence of Lewis’ plot is preserved, the themes and ideas behind the story are largely lost.

If the first Narnia film got perhaps two-thirds of Lewis’ intended meaning, Caspian is lucky if it gets a quarter. That may not directly detract from its merits as escapist fantasy, but Lewis fans with regrets about the first film will feel betrayed by the second — and not just because events have been changed.

Perhaps most damagingly, the filmmakers eviscerate the crucial theme of skepticism about the existence of Aslan and the Kings and Queens of Cair Paravel, as well as the whole world of Dwarfs, Talking Beasts and spirits of wood and water.

No longer do we see Caspian’s nurse dismissed for telling Caspian stories of Old Narnia, or his tutor Dr. Cornelius daring to instruct him in these matters only in private. This might not matter so much if the film had other ways of making the point — but it doesn’t. The notion that stories of Old Narnia are anathema in modern Narnia is simply dropped.

Worse, Trumpkin the dwarf (Peter Dinklage) — in Lewis an archetypal lovable skeptic whose heart is better than his head — no longer shows any sign of disbelieving the old stories. This Trumpkin appears to believe that Aslan and the Pevensies were real in their day, but abandoned Narnia long ago, leaving the Narnians to fend for themselves.

Almost as diminished is the theme of faith and sight, with faith opening one’s eyes to the extent that one believes.

We do get the scene in which Lucy sees Aslan when no one else does — but not the rest of the story, in which Aslan is at first invisible to the children until one by one they begin to see him in proportion to their openness and willingness to see him.

Hidden as Aslan might be in the book, he’s hardly in the film at all. Visually, Aslan is more impressive than ever. Even close-up, with Lucy embracing him in the woods, he looks utterly real and warm and solid. Yet the filmmakers turn this crucial meeting into a dream sequence, deferring the dialogue and Aslan’s active presence until the very end. In the book, he’s invisibly present, leading the children; here he doesn’t seem to be around at all.

As in the first film, whether deliberately or cluelessly, Aslan’s dialogue has been altered in ways that subtly un-divinize him.

In Lewis’ Caspian, when Lucy notices that Aslan seems bigger, Aslan is quite clear that it is not he who has grown; rather, paradoxically, because Lucy herself is older, he seems bigger to her: “I have not [grown]. … Every year you grow, you will find me bigger.”

In the film, he says simply, “Every year you grow, so shall I.” This subverts Lewis’ point about the infinite mystery of God, which as we grow is always revealed to be greater than we previously supposed.

Likewise, when the film’s Aslan tells Lucy that “we can never know” what would have happened, Lewis aficionados will wince at the slur to Aslan’s omniscience. In the book, the line is “No one is ever told” what would have happened, with no implication that Aslan himself doesn’t know — only that he’s not telling.

Perhaps the most glaring omission is the absence of Bacchus and the whole mythological riot of the final act — the climax of the book’s theme of the vindication of mythic imagination over Enlightenment rationalism.

The upshot is that Caspian is a good-looking fantasy film with some appealing eye candy and comparatively little to do with the book, beyond basic themes of good vs. evil and rather generic faith. More inspired by the book than adapted from it, Caspian is most likely to appeal to those not especially attached to the book: a lesser work flanked by two more popular tales.

If the same team were going on to Dawn Treader, I would be about ready to throw in the towel. Happily, director Michael Apted (Amazing Grace) is slated to take the helm from Adamson.

I have no idea whether Apted is the right director for this material, but I don’t even want to think about how Adamson and company would dumb down Eustace Scrubb or the Dufflepuds. The Narnia franchise desperately needs an immediate infusion of new blood; we can only hope it is the right type.

Steven D. Greydanus is editor

and chief critic of DecentFilms.com.

Content advisory: Much fantasy action and violence and some menace to children, including fairly intense battle sequences; mild adolescent flirtation and a brief kiss.