The documentation for the XML structure, i.e. which tags go where (e.g. chapter into book, page into chapter...) and what attributes are possible (e.g. background color for pages, path to images to load...)
The source code documentation / API, if you wish to interact with the engine inside loaded swfs or when using the sources to create a new instance of the engine in your code environment.
The XML used to generate the demo on the homepage, because examples are always better than theoretical explanations.
An XML validation service, so you can check your XML for errors if something does not work as expected or the engine can't load the XML.
TortoiseSVN, a SVN client, may be used to access the latest development version of the engine using
this URL.
FlashDevelop, a great ActionScript IDE when working on pure code, to get around the gruesome code editor that comes with the Flash IDE.
Notepad++, a great, free tool for editing your XML files if you don't have Dreamweaver (which is a little superior here, because it provides autocompletion based on the DocType Definition).
