Having your book edited by a professional is extremely important. Editing can make or break a book. It is the difference between people focusing on your story and being distracted by poor grammar or typos, to the point where they stop reading.
If you personally know a professional editor, go with them! If not, get a couple of referrals from authors you know, a publisher, friends, or ask your social media following, and get a couple of editing quotes.
Be very careful about just going with either the cheapest (price-conscious) or most expensive (perceived value). Make sure you actually speak to the editors and get a feel for them. Have either of them edited books in your genre before? Do they seem excited to work with you? Do you feel like they just “get” you? What is their editing process? How involved will you be? Do you feel comfortable with that process?
Ask questions. You want to work with an editor that you truly feel will make your book better, not someone who will make big changes to the structure without talking to you first.
Editing is what will make your book go from good to great. Your editor will point out inconsistencies that you miss because you’re too close to the material and have read it so many times. They will find typos, fix grammar, and help you with making sure you are not using the same adjectives over and over.
This is a very important step in the process of publishing a book and should not be skipped.