Originally Posted by dgatwood
For a small document, sure. But books can handle more than that because of their size. For example, your title page need not use the same font as other pages in the book. Your chapter heads often get significantly different styles. Drop caps. Small caps. Heading along the top. And you're right at six without doing anything even remotely fancy with the body text, sidebars, etc.
I would consider Each 'EPUB Page' within a book a 'Document'
Most chapters have how many different?
the basic body text
Special-case text: Ransom notes, headlines...
In many cases, they are just a size/weight change, not a separate face.