I agree with my esteemed (
) colleagues as well. The first part of the help should ensure the user knows exactly what he or she has purchased and it will run on their hardware. It should then outline how to install the software (if not already done of course), then a short tutorial on opening and navigating your first ebook. More detail, like fonts, margins, bookmarking and other fancy stuff can come after this, but making a good first impression with the reader software should be important, as this impression is often the one that sticks...
Craig.