Read This First
You need an editor
You need a copy editor
These cannot be the same person.
I’m putting those three sentences before all other content because they are the most important concepts I need to convey. Even before I start talking about the risks and benefits of publishing options, I want you to be aware of what you absolutely cannot do without.
The reason they cannot be the same person is a matter of perspective. You want your content editor to be concerned only with what you write about and how. Good copy editors are detail oriented and very skilled at catching missing commas and the like. But if you want to give them the best chance of success they need to see your final version for the first time.
Once you’ve worked with an editor he’s invested part of himself in your work. He may have gone over several drafts with you. After he has become involved it would be all too easy for him to miss mistakes because he knows what should be there.
A copy editor, however, is only required to care about the presentation. I’m sure copy editors would prefer to actually like the book they are combing through. But they are reading your work with a different goal in mind and that needs to be clear from the start.