There are three types of book editing and you need a different editor for each type
Every book needs three basic types of editing, and each type of edit requires a different editor.
1) Development Edit: The developmental edit, sometimes called substantive or comprehensive edit, is the big picture stuff. Basically it asks the questions, does the book flow? Does it work? It addresses style, organization, and overall readability. For fiction this means the story arc and related elements; for nonfiction, it means the central theme and supporting materials. What’s getting in the way of this? Are there roadblocks or detours? Does the writing veer off course? What sections will confuse, bore, or frustrate readers? Until the developmental edit is complete—and the needed adjustments made—it’s a waste of time, money, and effort to move on to the next two types of edits. Always do a developmental edit first.
2) Copyedit: The copy edit, sometimes called a line edit, looks at paragraph structure, sentence construction, and word choice. Don’t do this until after the developmental edit and always before hiring a proofreader.
3) Proofreading: A proofreader looks at grammar, punctuation, and typos. A proofreader scrutinizes every word, the space between them, and how they’re connected.
Editors usually specialize in one area or another. Even if they do more than one type of editing, they can’t do all three types on the same pass. So if you find one editor who will do all three, it will still require three edits, not one.
Usually, you need to hire these people. If someone gives you free editing, you often get what you pay for. And finding an English major or someone who likes to read does not make for a good editor. Always find someone with editing experience. Though every editor has to at one time do his or her first edit, don’t let it be on your book.
When I read self-published books they too often fall short, and most all of the time it’s because of editing issues: no editing, poor editing, or inexperienced editing. Or they didn’t have all three types of editing. And sometimes traditionally published books suffer the same fate. Though they have been edited, it wasn’t good enough.
Don’t skimp on the editing. Your book will suffer if you do.