The story picks up where the previous one left off: two boys Walter and Danny discover the Jumanji board game where it was hidden and take it home. However, Danny discovers another game also hidden inside the box: the sci-fi-based Zathura. Despite their ongoing rivalry, Walter and Danny find they must work together if they're ever going to beat the game and get back home.
This book contains examples of:
- Artifact of Doom: The board game Zathura, while not inherently evil or malevolent, still rains down misfortune and disaster on the players in the form of meteor showers, invading aliens, and black holes. The only way to get rid of them is to finish the game (assuming it hasn't killed you first). However, even if the heroes do manage to finish and dispose of the game, more often than not it will just worm its way into the hands of another group of unfortunate saps.
- Contrasting Sequel Main Character: Walter and Danny have a tendency to start games without reading the instructions, unlike Jumanji protagonists Judy and Peter. They are also more prone to arguing.
- The Game Come to Life: Walter and Danny are transported into the world of the game.
- The Game Plays You: The game affects reality and can only be survived by playing to the end.
- Win to Exit: Players are trapped in the game until they win.