Absolutely, Tom. Encrusted oldie, I like that one. Thanks for your thoughtful and positive comment. I think the heavier the editing, the more important confidence with a genre or niche is. For a developmental edit, I’d want someone with specialty experience in my genre, whereas with a proofread, I’d be comfortable with pretty much any competent editor.
You might hire someone for a proofread, but let the editor know that you’re open to hearing from him or her if the work needs a heavier edit. The editor would need to present you with evidence in the form of sample pages that showcase what’s needed—and your job is to make sure you agree. You want to feel like an editor’s edits are polishing your work and making it shine. If you feel dread or anger, or even if you feel misunderstood, it’s likely not a good fit. At the very least you want to share your reactions with the editor so they can respond or change course.
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There seems to be something half-way between beta-reading and development editing. I think it’s right for many new writers — I’m just finishing my first book, and was not about to pay a real development editor, but beta readers weren’t engaged enough (especially friends unwilling to point out the negatives). But it this kind of editing doesn’t really have a clear name.
I cannot speak for all editors, of course, but I know I and many of us would be open to editing just part of your book at first, say, a particular chapter or two that you sense needs a lot of work. That is often enough to show you mechanical errors that you tend to make repeatedly. You can then go through the entire manuscript yourself looking for as many of the same kind of errors as possible. You will sharpen your basic writing skills in the process, and it will pay off in all future projects.