A Story Engine, much like a Game Engine, which is software used to create and run Video Games, is software used for reading and writing Gamebooks. The software is much like an Ebook Reader, and pauses in between chapters, to wait for the reader's choice. A Story Engine is different from a Solitaire, as you can use it to create Gamebooks, whereas you can only read one using a Solitaire.
Software
An example is PlayStory, a Story Engine which can be used to read the stories, called Play-Stories by the software, and to write such interactive Play-Stories, using the PlayStory Developer.
Another is The Gamebook Engine, a highly advanced engine with multiple features, and runs on Hyena script. This, too, needs no knowledge of computer programming.
References
Story Engine Wikipedia(Text) CC BY-SA