Mario, Luigi, and Princess Peach travel to Yoshi's Island for a playful visit, but Bowser interrupts by kidnapping Peach. Mario and Luigi set out to rescue her, and Donkey Kong joins the chase. However, Donkey Kong is tricked into eating a banana offered by Bowser and becomes the koopa king's minion. He leads the plumbers to a giant fountain where they see what appears to be Peach, only to discover a doll holding a letter from Bowser declaring they are in Hell's Donkey World. To break Donkey Kong's forced loyalty, Mario and Luigi must find a rainbow banana hidden at the bottom of the ocean. King K. Rool later teams up with Bowser, taking Luigi hostage to set a trap for Mario and his allies.

In the second book, Mario and Donkey Kong return to Mario Land after their long journey and find Princess Peach and all their friends turned to stone. Clues point to Kaptain K. Rool and his crew, so they travel to Kremling Island in Donkey World. There they free Diddy and Dixie Kong from a chest, but K. Rool brainwashes the two young apes, turning them against Mario and Donkey Kong. The heroes must reverse the petrification and defeat the brainwashed Kongs and their crocodile captors.

The story is told through a mix of narrative and interactive activities such as puzzles, mazes, spot-the-difference games, and picross challenges. The main characters are Mario, the courageous plumber; his cautious brother Luigi; the powerful but easily manipulated Donkey Kong; Princess Peach, the kidnapped ruler; Bowser, the primary antagonist; and King K. Rool, who serves as a secondary villain. The setting spans the Mushroom Kingdom, Yoshi's Island, the bizarre Donkey World, and Kremling Island, drawing from Super Mario World, Donkey Kong Country, and Donkey Kong Country 2: Diddy's Kong Quest.