The goal of this jam is to make an Adventure Gamebook, these are much like the interactive fiction you know, but will often have more traditional RPG elements such as asking players to write on a character sheet or roll dice.
Twine is an excellent tool for writing Interactive Fiction, and if you want your twine story to appear like a classic printed gamebook, you can use the WritingFantasy story format which will display all of your passages in a shuffled order and format links between them appropriately.
There is no theme, but if you would like one, roll 1d6:
Note: Be mindful that the term "Choose Your Own Adventure" is a trademark which is defended vigourously!