Just to add to the last post, I can't tell you how many people begin their conversations with me by saying that they've had all their friends, family, and co-workers read their work and have received grand reviews so the work doesn't require much editing (this is for the editing jobs on books by new and unpublished writers).
I can't stress enough how little these opinions mean (sorry) and how very unhelpful they are (when your aim is to truly improve the piece). You will not receive the same input from these folks as you would from a trained professional. They won't be able to help you with the finer details of improving the flow and cohesiveness of a story and they won't know how to guide you with improving characterization, plot, pacing, dialogue, theme, setting - all of the elements that combined make up the story.
