Nintendo Adventure Books: Monster Mix-Up DS is a digital version of the gamebook of the same name written by Bill McCoy and published by Archway Paperbacks in 1991.

It is best described by the book’s introduction:

“Dear Game Player: You are about to guide me through a great adventure. As you read this book, you will help me decide where to go and what to do. Whether I succeed or fail is up to you. At the end of every chapter, you will make choices that determine what happens next. Special puzzles will help you decide what I should do—if you can solve them. The chapters in this book are in a special order. Sometimes you must go backward in order to go forward, if you know what I mean. […] Good Luck! Driplessly yours, Mario.”