As mentioned in a previous post, Varytale is a platform for interactive stories. It’s put together by Ian Millington, the same person who created the Undum tool, but Varytale goes quite a bit further.
Writing Tools
Undum provides a slick front-end and a way to build a few choices and otherwise leaves everything up to the author (hey, you don’t mind learning some javascript to code your story, do you?). It’s been used for a couple of neat IF works, including Deirdra Kiai’s 3rd-place Comp 2011 winner The Play and Andrew Plotkin’s The Matter of the Monster.
By contrast Varytale comes with a complete authoring tool; a website where books are showcased and attractively presented online; the capacity (eventually) to use one of several payment schemes to charge for content; and feedback and statistics tools that allow the author to collect ratings and comments on content, and to see which story choices are especially popular or unpopular. These tools require vastly less coding than traditional interactive fiction, but they do allow for world state and player stats-tracking. (Some time back, I described why CYOA without world state is a bit too restrictive for most of what I want to write.)
Emily Short's Interactive Storytelling 