Every time I finish editing a book, I make sure every word, every phrase is complete and polished, check to ensure the story flows so readers will be hooked, dot every "i", cross every "t", give the manuscript a (symbolic) kiss, and wish them luck. No one knows how that book will do when it finally appears in public.
But it takes a brave soul to put it out there. And it takes both a brave and a smart soul who shows they care enough about the final result to hire an editor before just going ahead and pressing "Publish". Self-publishing is easy. Anyone can do it. It's easy to type, easy to blather on about whatever, easy to press "Publish" on any one of the self-publishing sites. But once that book is out there, it's out there. And if anyone reads that book, they'll remember if the author was good, bad, or indifferent.
We don't want that. We want everyone to remember our book as being the BEST. We want them to wring their hands, dying to get their hands on the next one.
I'd never send my kids to school half-dressed or unfed. I'd never allow a kid to head out into public with bad manners or lack of respect for those around them.
I'd never publish a book which hadn't been professionally edited and obviously treated with love. I respect readers and book buyers. Books take time and money to read. I wouldn't waste their time.
Don't waste your talent. If you've written a good book, let an editor make it the best it can be. Doesn't have to be me. There are a lot of excellent editors out there. Get referrals, read testimonials, check out the edited books. This is a major commitment and deserves just as much time and deliberation as you spent writing the book.
You owe it to your book. You owe it to yourself. You owe it to the publishing world in general —too many nasty, unedited books are out there, making readers question the quality of all writing.
Hire an editor.