Twine is a popular tool with robust online documentation. For more information about using Twine, including its more advanced and customizable features, check out:
The homepage providing access to Twine online, Twine download options, the Discussion Board, Chat, Cookbook, and Wiki. It also provides examples of published Twine stories available online.
The Twine Cookbook
A quick reference guide proving examples and code for common questions and editing needs. Maintained by Twine.
The Twine Wiki
A robust wiki page with tutorials and reference documentation for Twine. Maintained by Twine.