“Bridge to Terabithia,” if the previews are to be believed, is a fantastical Narnia-esque tale of two young adventurers discovering uncharted lands inhabited by fierce and benevolent CGI creatures who take them away from their ordinary lives. Fortunately, previews lie.

In reality, the film tells the story of a girl, Leslie Burke (AnnaSophia Robb), who brings creativity and sensitivity to the life of Jesse Aarons (Josh Hutcherson), an artistic, isolated boy. Based on Katherine Paterson’s childhood staple of a novel, it is also a gentle introduction to puppy love and loss.

Jesse and Leslie become friends after Leslie delivers an imaginative essay in class. The much-anticipated special effects make their first unnecessary appearance here — during Leslie’s description of a scuba-diving trip, bubbles float out of her mouth and fish swim past Jesse’s eyes. That aside, Jesse’s recognition of the same spark of invention he’s been striving to express and the conviction of Leslie’s imagination brings them together to establish their forest hideaway, which Leslie christens Terabithia.

Director Gabor Csupo, of “Rugrats” fame, brings the same sense of childhood wonder to this film as he does to his cartoons. The screenplay, by Jeff Stockwell and the author’s son David Paterson, captures more of the awkwardness of early adolescence than the drive and flow of the original narrative.

The filmmakers opted to modernize the film rather than present it in its original 1970s context, and the concept on the whole is jarring. The cars, museum exhibits and Leslie’s fashion choices (courtesy of costume designer Barbara Darragh) are modern. But the Aarons family and overall ambiance of the location is dated (and more appropriate for the book). The production team and directors didn’t commit to a specific time and place, which made these aspects distracting.

The child actors are captivating; Robb makes for a bubbly, engaging Leslie. Her tendency toward sugary sweet facial expressions and vocal inflections is countered by the delight she takes in exacting revenge on class bully Janice Avery (Lauren Clinton), and perhaps by the memory of Robb as the hellacious gum-cracking Violet Beauregard. Hutcherson’s Jesse is by turns stormy and exhilarated. He resents his father’s brusqueness and lights up under the more encouraging attention of Leslie and Ms. Edmonds (Zooey Deschanel).

The filmmakers handle the tragic parts of the book in an almost detached manner, viewing the events, as the novel does, entirely through Jesse’s lens of denial. This approach makes sense because it allows the viewer to experience the stages of grieving as gradually as Jesse does.

The majority of the special effects in the film seem to evolve organically. Jesse’s and Leslie’s imaginations turn an ordinary squirrel into a creature half rodent and half bully, and the animation reflects that transformation. Trees become giant trolls and dragonflies become warriors — and the result is predominantly enchanting. When the kids run through the woods, their sense of excitement and confidence makes them run faster than the wind.

It is the film’s closing shots that ultimately render the CGI overdone. The greatest strength of “Bridge to Terabithia” in novel form is the counterpoint between the personal growth the children achieve in their imaginary world and the way they transfer that newfound courage to real life. Csupo’s attempt to place the final emphasis in the fictional dream world undermines that maturation.

Still, at its heart, “Bridge to Terabithia” is successful, with just the right level of drama to give children a challenging cinematic experience, but not so much they’ll have nightmares. The sweetness and nostalgia will have grown-ups wishing they could relive their memories of tree houses, first best friends and fantasy worlds of youth.

“Bridge to Terabithia” was written by Jeff Stockwell and David Paterson, and directed by Gabor Csupo.

“Bridge to Terabithia” received 3 1/2 out of 4 stars.