From the back cover:
Blendin Blandin is searching for the legendary Time Pirates’ Treasure, and he needs Dipper’s and Mabel’s help... and yours, too! Journey through time and explore the dragon-infested medieval era, the Weird-and-Wild West, and the laser-and-giant-baby-filled future. YOU choose from multiple paths that lead to different wacky adventures! You might end up finding the greatest treasure ever known, or you could send Blendin and the twins into an abyss from which they will never return!
This is a Disney-produced “Select your own “Choose-Venture” book which is a comical take on the traditional Choose your own Adventure concept.
Based on the TV series created by Alex Hirsch.