C.S. Lewis' The Lion, the Witch, and the Wardrobe—the most famous book in his revered, Christian-flavored The Chronicles of Narnia fantasy series—sounds like the ideal multiplex offering: a family friendly mix of fantasy filmmaking, literary heritage, and Happy Meal tie-ins.

Hence Hollywood's long-awaited The Chronicles of Narnia: The Lion, the Witch, and the Wardrobe, in which four British children—Peter, Susan, Edmund, and Lucy Pevensie—flee the WWII bombings of London for a country mansion. Discovering an enchanted closet that serves as a doorway to Narnia (a fantastic world of talking beavers, stunning magic, and loads of plasticine CG), the four soon meet a majestic lion, Jesu—er, Aslan (voiced by Liam Neeson)—and start waging a war against the evil White Witch (Tilda Swinton).

Narnia tries hard to be those two important things for a fantasy film: transporting and impressive. And, to director Andrew Adamson's credit, it occasionally succeeds. But largely, Narnia feels smallish and artificial; it's neither as vast as J.R.R. Tolkien's Middle-Earth, nor as interesting as one of J.K. Rowling's musty classrooms. Indeed—more than any line of dialogue or any theme from the Enya-ish score—the thing that sticks throughout Narnia is what Tolkien, Lewis' friend and colleague, reportedly said after reading a draft of Lewis' novel: "It really won't do, you know." Dubious at the time, now—and in reference to the Narnia film—that line's self-referentially damning: After Peter Jackson's Rings trilogy and at least one decent Harry Potter adaptation, moviegoers are used to better fantasy films than this.

It's easy to blame Adamson (whose previous directorial experience consists of the annoyingly hyper Shrek films), but other culpable parties are the sluggish script and uneven casting. In the book, the Pevensie children carry the plot, but here, the stiff-lipped Peter and Susan (William Moseley and Anna Popplewell) feel more like parodies of British kids than actual ones; Edmund (Skandar Keynes) is nauseatingly smarmy and simplistically villainous, and Lucy's so adorable that one suspects actress Georgie Henley might be the product of a genetic experiment to yield the world's most precocious child. These, as practically the only non-fantasy entities in the picture, are the characters that supposedly serve as the viewer's link to the film. They fall flat.

Never is this emphasized more than whenever Swinton's onscreen, leading her armies of trolls and ogres. The devilishly designed villains tear Narnia apart with a contagious gusto, and it proves easier to root for the White Witch's Creepy Forces of Evil than for Aslan's Goody-Two-Shoes Forces of Boring—each of Swinton's hammy sneers is twice as fun as the messianic poses Aslan's so fond of striking.

That is, until the film's climax—a massive battle on a sunlit field, where fantasy creatures tear at each other and the Pevensies finally nut up and do something other than whine or look wide-eyed. Adamson proves surprisingly adept at this rousing, epic finale—just as the picture's wrapping up, he treats moviegoers to a hint of why a Narnia film seemed like such a great idea. Too bad it takes so long to get there.