Those who criticize "Zathura" for being a copycat "Jumanji" are apparently clueless about the Van Allsburg's books. "Zathura" is a sequel to "Jumanji", it is about what happened when the Budwing brothers opened the game box that Peter and Judy discarded at the end of "Jumanji". Early board games were often designed with two-sided boards so that the game pieces could be used to play two different games-usually of the same type. "Zathura" was the flip side of the "Jumanji" game board and the ones the brothers chose to play (because Walter did not like jungle games). So it is "supposed" to be like another "Jumanji".
Having grown up with this same sibling age dynamic (six and ten) I was not surprised at the amount of yelling, anger, and resentment that goes on between the two brothers. I was however surprised that anyone would find this sort of thing entertaining. While their divorced father (Tim Robbins playing the only sympathetic character in the film) is away at a meeting, the younger brother (Danny) finds an old Zathura game in the basement. Based on those old 1950's tin toys it involves two tin spaceships on a track racing around space. Each spin of the dial determines the distance the ship will move on that turn and a card is ejected detailing what happens to the ship at that point of space.
As Danny and Walter face the challenges of space they discover that they can work as a team and they even develop some affection for each other (a more unrealistic idea than anything they actually encounter in space).
Like the source book, the movie adaptation of "Zathura" targets kindergarten to Grade 5 children. Like "Sharkboy and Lavagirl", older viewers will find very little of interest other than a fun production design and nice effects.
Unfortunately "Zathura" it is not as pure as "Sharkboy and Lavagirl", which uniquely refused to compromise its "for kids only" story. "Zathura" does compromise, as the producers attempt to expand their audience by creating an older sister (Lisa played by Kristen Stewart) who was not a character in the book. While Stewart is fine in this role and even provides some comic relief, it is rather disturbing that the producers chose to turn her into a pubescent sex object, blustering around the house in her underwear for most of the film. Van Allsburg's illustrations are the best part of his books but a "hot teenage sister" is not an image he has ever published.
Then again, what do I know? I'm only a child.
