DUNILOG is a dialog engine that is designed to make dialog based games easy to create.
It is possible to make games with nearly no programming knowledge and it is very easy to extend for programmers.
Read the forum post
Workflow:
Create your story by building up scenes, actors and statuses in a node based editor.
Your story gets rendered as a prefab - drag it in your scene and press play.
You can skin your GUI by just adding a unity GUISkin file and use the layout settings.
You can hook into each node to trigger your game logic and visuals.
For programmers you can also use the event system to react to the story and create complete custom UIs.
DUNILOG includes a full example project to get you easily started.