"Behind every great man is a great woman." An equally true idiom may be "behind every great writer is a great editor." Most writers feel like they don't need an editor, and this may stem from some insecurity about being critiqued. Let's pause there for just a second, though, because if you're worried about negative critiques, writing is probably not the thing for you. Writers inherently open themselves up to public critique and judgment the moment their book is published. This is precisely the reason you need an editor.
My job as an editor is to critique your work, yes, but also to elevate it to the work that it has the potential to become. Professional editors have the ability to not only look at the big picture of the book and find imperfections in cohesiveness, plot, pacing, characterization, organization, etc., but can also look at the minutiae of grammar, spelling, and punctuation. Even the worst typos can be forgiven if the book is an amazing read, but if you have issues with any of the aforementioned "big picture items" your book will be an immediate flop.
As editors, our job is to find and pull out nuggets of truth, unique facets of your book that help make it marketable and relatable to your audience. It may seem odd to have a favorite editor, but being an editor that may not seem quite to strange. Mine is Max Perkins; not a household name, but his authors certainly were. Perkins worked with both Hemingway and F. Scott Fitzgerald, to name only two. He was quiet but powerful in the stroke of his pen. “His essential quality was always to say little, but by powerful empathy for writers and for books to draw out of them what they had it in them to say and to write.” This, then, is the chief responsibility of a professional editor. We offer new perspectives and when coupled with the voice of experience for a novice author, we offer an invaluable contribution to your manuscript.
I hear several things in regard to editing. Mostly when I ask someone if their book has been edited, the answer is my [mom/sister/aunt/brother/former English teacher] edited it already. No. Unless they are a professional editor who works with the Chicago Manual and has experience in book edits, this isn't sufficient. More on this later. I also get asked several questions about editors: When do I hire one, how do I find one, and how much does it cost? All excellent questions. I'll answer briefly here, but look for more expansive answers on these topics in the near future. You should hire an editor when your book is in it's most complete state. That means you've done multiple drafts and self-edits and you have probably had it read by a beta-reader. If you send your first draft to an editor, you're wasting both their time and your money (this is what author coaches and beta-readers are for). As far as hiring an editor, there are multiple resources online such as Indeed.com, Fiverr.com, IAPWE.com, and even occasionally on Craigslist. My best advice is to find an author or group of authors and get recommendations for editors that they have worked with. The cost is often dependent on the editor and their workload. Most editors charge per page or per word, and will charge more depending on how technical the document is. Almost every editor I know does a free editorial sample, so be sure that's offered. Always ask what style guide they use, and if they don't know what that is, Run Away!
At the end of the process, your editor knows your book just as well as you do, and wants to see you be successful. We are your confidants, collaborators, therapists, accountability partners, and biggest cheerleaders. Who wouldn't want that kind of support?
Happy writing!