Zathura is a spinoff of Jumanji  The original Jumanji movie stays close to the original book.  Zathura was also made into a pretty fun movie, but there connection to Jumanji was never made within its plot.  And the movie is quite a bit different from the book.  Two brothers are playing outside and discover the game Jumanji.  However, it contains a second board with a trip to Zathura.  The boys begin to play, and just like Jumanji strange things start to happen.  The house ends up in space, there is a meteor shower, and robots come to life to kill aliens.  However, the moive goes about an hour longer than the book.  In the book, the oldest brother is sent back in time 5 hours and the story ends with him NOT playing the game.  While I did like the book, this is one time I can say for sure the movie was better.