Imagine being an author, writing a book and toiling away in solitude.
You’ve got a general idea for the overall subject matter that’s good, but of course that idea has to be executed on chapter by chapter.
How would you know if one of those chapters sucked?
I suppose if you had a really good, attentive editor, she might tell you. But that’s a luxury that even most published authors don’t have.
So, in all likelihood, you just wouldn’t know.