You know, there's a number of authoring packages, but if you want cross platform compatibility, you _could_ always make it HTML based. If you're just using static documents and client side scripting, you don't need a web server.
Several years back we produced a product demo CD for a client, and used a full on compiled language, but it was OS specific (Winders© only) and required an install, plus additional runtime installs.
A few years after that, they wanted to do an all new version of it, on DVD (with much more multi-media content) and we did it all in HTML and Javascript, and it was nice because no install, simple development, etc., and as a perk, it could be easily deployed to the web. At the time there were a couple of pretty good JS DB runtime engines too, so it was totally searchable, extensible, etc.