I will avoid talking about plot in terms of creative writing, there are far better sources for that. Rather I will focus on how the gamebook's strict branching tree format needs to evolve to facilitate better interactive storytelling.
Gamebooks plots are a string of set-pieces.Simple gamebook plots are often a sequence of interconnected set-pieces. The player moves from scene to scene, the designers assuming that ‘kill the wizard’ or ‘progress through the map’ is a robust enough premise to glue the narrative together.
Although fun, these simplistic romps lack genuine causality. They defy the definition of plot: a causal sequence of events that make up a story. As E.M. Forster explains instead of "The king died and then the queen died" it's better to create a causal relationship between the two events, for example "The king died and then the queen died of grief." Events need to unfold in a logical chain, to create narrative momentum, and pull the reader along with them.