An author needs to engage a writer till end of the writing else is deemed a failure.
Sustained interest in a book or love or romance or even a project or organization or country happening is possible by following points
1) bring in innovation at strategic juncture.
2) develop the theme so well that people get involved and emotional about the purpose
3) have short time boxed closures to an episode or incident. don’t drag on that.. (be it arguments, be it conflict or be it even a moment being depicted in story)