You could try an FSM with a new state for each story point, which would connect to each other through events which directly correspond to choices the player makes. The FSM interface in PlayMaker actually reminds me a lot of a choose your own adventure map, even when it's being used outside of this context.
As Jean said, this sounds like a big undertaking. You would need to stay very organized! Here's how I'd get started:
Level Check/Loader FSM: Scene 1, (in addition to whatever you have going on for the start of the game), have an FSM which handles the story map. State 1 of this FSM would check every frame for an integer change (let's call the int pathnumber). This level loader FSM would need to persist throughout all the scenes/levels - either make sure it's a part of each new level, or enable "don't destroy on level load" for this FSM.
On change, it would pass to a new state which would check for what number the pathnumber int changed to. You would have a separate action on this state for each unique path/story choice. For each pathnumber, the FSM would pass to a new state to load the matching scene/level number. (each of your scenes/paths will need to be a new level in Unity) After level load is complete, iw dould return to the idle state where it waits for pathnumber to change.
Dialog/Story/Path FSM: You would create a separate FSM within Scene 1 (and each new scene) to handle dialog/etc that drives the story. As soon as the player chooses a path (by clicking dialog, entering an area, etc), this FSM would change "pathnumber" to the appropriate int. Let's say the player walks into a cave and you've decided the beginning of the cave scene is Path 16. This FSM would set "pathnumber" to 16, triggering the level loader FSM to load a new level (level 16).
Within level 16, you'd have a new dialog/story/path FSM to give options for the player choosing more paths specific to that scene.
It's quite a complicated setup, but I think it would work well if you stayed organized! Good luck