What do editors do? More important, what can your editor do for you?
This first in a series of posts is about substantive/developmental editing, which is my specialty.
Unless you are extraordinarily blessed, you probably are stronger as a writer in some areas than in others. A professional editor should not only point out your strengths and challenges, but also should help you triumph over your challenges by showing you how to expand your own strengths and talents into areas of the book that need them.