In the realm of recent fantasy films adapted from popular books, "The Spiderwick Chronicles" doesn't hold a candle to the "Harry Potter" series, 2005's "The Chronicles of Narnia: The Lion, the Witch and the Wardrobe," or 2007's grievously overlooked "The Golden Compass." On the upside, it is easily superior to 2006's "Eragon" and 2007's "The Seeker: The Dark Is Rising." These comparisons should serve more as a genre litmus test, for what the picture really resembles is 1995's "Jumanji" and 2005's quasi-sequel "Zathura," both imaginative and ambitious efforts about board games that come to life. As directed by Mark Waters (2004's "Mean Girls") and based on the children's books by Tony DiTerlizzi and Holly Black, "The Spiderwick Chronicles" doesn't come alive in quite the same way, its simplistic and occasionally juvenile plot at odds with its more mature subject matter involving a family going through a traumatic divorce.

That family in question are the Graces—newly single mother Helen (Mary-Louise Parker), teenage daughter Mallory (Sarah Bolger), and twin sons Jared and Simon (Freddie Highmore in dual roles). As they move into an old and empty country home that previously belonged to their great aunt Lucinda (Joan Plowright), Mallory and Simon try to stay supportive while the rebellious Jared can't help but resent his mom for tearing him apart from his dad (Andrew McCarthy).

On their first night in their new dwelling, Jared discovers a dumbwaiter hidden in the wall that lifts him up to a hidden attic. It is here that he discovers "Arthur Spiderwick's Field Guide to the Fantastical World Around You," written eighty years ago by their great-great uncle (David Strathairn). Once opened, it unleashes a world of mystical creatures outside their home—among them, goblins and trolls ruled by giant shape-shifting ogre Mulgarath (Nick Nolte)—who will stop at nothing to obtain the book and rule the universe. It is now up to Jared, Simon and Mallory to join together and find a way to destroy the writings before Mulgarath snatches them.

Written by unlikely trio Karey Kirkpatrick (2006's "Charlotte's Web"), David Berenbaum (2003's "Elf") and indie-stalwart John Sayles (2004's "Silver City"), "The Spiderwick Chronicles" is a family film that mishmashes childish humor and inane story points with mature thematic elements and more effectively scary moments than the recent U.S. remake of "The Eye." What audience, exactly, director Mark Waters is targeting is never made clear. On the one end are goofy hobgoblin Hogsqueal (voiced by Seth Rogen) and honey-loving house elf Thimbletack (voiced by Martin Short), comic relief that isn't particularly comic or a relief. The rules established inside the field guide are silly and convoluted even for a fantasy movie. Would you believe that tomato sauce, of all things, kills goblins, and earthly people are only able to see the creatures with the naked eye if Hogsqueal spits in them?

Once the imposing Mulgarath—looking like a cross between one of the tree people from "The Wizard of Oz" and Satan—and his minions begin their attack in earnest, "The Spiderwick Chronicles" raises in intensity and becomes rather creepy for a PG-rated picture. There are a number of suspenseful sequences, the best being a climactic showdown between Jared and Mulgarath. Meanwhile, the most purely magical moment, of which there are too few, comes when the siblings ride on the back of a flying Griffin (shades of Falcor from 1984's "The Neverending Story" are undeniable).

Those aforementioned scenes and more are good as special effects eye-candy, but the human story is left lacking in depth and insight. While it is appreciative for director Mark Waters to plant his characters in a real-world situation that crosses paths with a fantastical one, the strife and ultimate bond between sister Mallory and brothers Jared and Simon are unsatisfying. No fault of actress Sarah Bolger (2006's "Alex Rider: Stormbreaker"), who is fine with what she is given, but Mallory is written as a screechy brat who is difficult to like. Freddie Highmore (2007's "August Rush") is excellent in the challenging roles of Jared and Simon, two separate people with distinct personalities. Perhaps due to the logistical nightmare of using a single actor for the part of twins Jared and Simon, these two don't share nearly enough scenes or dialogue exchanges for their relationship to feel authentic. It is also far too obvious when a double stands in for one of them in certain shots.

"The Spiderwick Chronicles" is flashy and diverting, but also ultimately insubstantial. The otherworldly conflict at its center should have served to compliment the story of a broken family coming together and realizing how valuable they are to each other, but this gets lost in the shuffle of a lot of chaos and chase scenes. Even the bittersweet last scene is undermined by a final shot of Hogsqueal delivering an out-of-place one-liner, further proving how erratic the tone is as it switches between kiddie comedy and more older-skewing drama and thriller elements. In need of surer-handed focus, "The Spiderwick Chronicles" held a lot of promise, but that promise is left unfilled.