The title says it is intended primarily for programming books. But what if some fiction writers discovered it and got creative? Who knows, the resulting novel might become a work art.
It's primarily targeted programmers. Because they are already familiar with Git/GitHub & Markdown and we have some "unique" features for programming tutorials/courses, such as interactive tutorials.
But you're totally correct, gitbook could and should be applied to many other kinds of writers. Markdown is a nice input format, and as soon as GitBook supports epub & pdf, other writers could use it for "production" quality books.
