The BFG Ruby Barnhill, Mark Rylance, Jermaine Clement. Directed by Steven Spielberg. Rated PG. Opens Friday citywide.

The BFG is one of those Steven Spielberg movies that practically assaults the viewer with wonder. Adapted from Roald Dahl’s beloved children’s book (originally published in 1982), it tells the story of a little girl named Sophie (newcomer Ruby Barnhill), who’s abducted from the orphanage where she lives late one night by a 24-foot-tall giant, after she spots him lurking in the streets outside. Luckily for Sophie, this particular giant, while big by human standards, is also friendly; she takes to calling him BFG, in fact, for Big Friendly Giant. Turns out the BFG (played, via motion capture, by Bridge of Spies Oscar-winner Mark Rylance) is actually the runt of his race, nearly as small compared to other giants as human beings are compared to him. He’s also the only giant who’s sworn off eating humans, which means that he soon finds himself compelled to protect Sophie from his hungry brethren—especially from the horrific Fleshlumpeater (Jemaine Clement).

For a writer best known for his children’s books (which also include Charlie and the Chocolate Factory and James and the Giant Peach), Dahl had a remarkable cruel streak, very much evident in his work. Spielberg, working from the final screenplay written by the late Melissa Mathison (The Black Stallion, E.T.), largely excises that quality from The BFG, skipping past the parts of the book in which giants munch on little kids as if they were mozzarella sticks. Problem is, this leaves a hole that he then has to plug with aggressive flights of fancy. The camera constantly swoops and plummets past and around the BFG’s giant possessions, as if his lair were the backdrop for an amusement-park ride (which it may well someday be). And the movie all but flatlines during an interminable sequence that sees the BFG take Sophie to an alternate world to gather dreams, represented here as wisps of pure light that resemble a generic screen saver.

Thankfully, the story takes a more absurdist (and Dahl-inflected) turn toward the end, as Sophie and the BFG enlist the help of the Queen of England (Penelope Wilton) in their campaign against the other giants. And while Barnhill belongs to the Hayley Mills tradition of spunky child actors who only vaguely resemble actual little kids, Rylance has a lot of fun with the title character and his unusual dialect, which includes lots of invented words like “gobblefunk” and “whizzpopper.” But Spielberg is at his best during quieter moments—for example, the film’s deft, silent opening, which demonstrates how a 24-foot-tall creature can walk the streets of London without (usually) being spotted. The more he insists on the importance of magic and dreams, treating them like a fireworks display, the less magical and dreamlike The BFG seems.