As a general rule of thumb, if there is no existing variant of a game that involves a board or cards, then it is most likely off topic on the Board and Card Games Q&A site.
If I understand correctly, a gamebook is a Choose Your Own Adventure-style book where you turn to certain specified pages to make choices. In that case, I would say that it would not be on topic. The criteria for whether a game is on topic is defined by these criteria:
- Be playable on or around a table
- Have objective rules of play and win conditions
- Offer dynamic challenges, either through other players, randomization, or both
- Be playable by hand, by human players implementing all of the rules
These game books fail one key criteria: they do not offer dynamic challenges. Every outcome is defined by the structure of the book, and if you know enough about it, you can predict the outcome of every choice.
I also think that, even in the case where multiple players are making choices, it is questionable whether the game is "playable by hand, by human players implementing all of the rules". Since the outcome of the game depends on hidden choices made by the writer that are represented in the structure of the book, then arguably those choices are part of the rules of the game, and human players would be unable to play the game without the book.