An excellent manuscript does not mean the book doesn’t need editing; it might require copyediting and proofreading as well. The main problem lies in the fact that these terms are frequently used as synonyms. Yet, while editing, copyediting, and proofreading are linked together, each one asks different questions. When a manuscript receives mixed editing services, it may have a major structural problem that is left unaddressed and instead time is used to fix minor punctuation errors in a paragraph that may be taken out later.
Editing is concerned with the book as a whole. The editor looks at the intended reader, the aim, the breadth of the book, the structure and flow and the clarity of the explanation. In a structural edit a chapter might appear late in a book; two sections may address the same content, and the conclusion may introduce new concepts. Editing isn’t focused on the commas; it is asking if the book functions as a coherent form of communication.
Consider reading a short section of a manuscript and trying not to correct sentences. Then write a comment by each paragraph that describes its role. Identify each paragraph as an introduction, as an illustration or as a transition. If you have two paragraphs with the same role, you have duplication. If you have a statement without any explanation, the book needs more content. This way you can view the book before getting lost in grammatical corrections.
Copyediting occurs after the larger structure of a book is established. A copyeditor is more directly involved with the structure of sentences, the terminology, the grammar, the punctuation, the capitalization and the internal consistency. The work may include tracked changes, queries to the author, and the use of a style sheet. The style sheet records choices made about capitalizing recurring terms, how numbers are written, and spelling in proper nouns and technical terms. Automated spelling-checkers can help with this process, but you will still need to make judgments since it is possible for a correction to be grammatically possible but to change the meaning of the sentence.
Proofreading comes later in the process and it begins once the copyedited text has been laid out and is part of the page proof or electronic file. The proofreader is looking for any remaining problems or inconsistencies, not starting the whole review from scratch. The proofreader looks for missing words, faulty punctuation, inconsistent heading styles, bad cross-reference, inaccurate image captions, repeated lines, incorrect folios, the table of contents is checked as well. In a designed publication there is also running heads, picture credits, margins, page breaks and other parts of the book that were not visible in the original manuscript and the proofreader needs to review them as well.
A single sentence can be addressed in all three stages. An editor may decide that the paragraph containing the sentence should be moved elsewhere in the book. The copyeditor may rewrite the sentence for clarity, query a potential problem in the fact, and add or delete a word in keeping with the house style. The proofreader may notice that in typesetting the sentence has been repeated, that one word has disappeared at the page break. The work in all cases is valid, yet it takes place at a different stage in the book-making process.
Pick a page and try the process a few times. On the first pass, think about the purpose, the order and missing content. On the second, think about sentence clarity and flow, consistency and the style sheet. On the third, consider spelling, grammar, the heading styles and the layout as well. Label each correction by editing stage. It is not important to get it all right the first time. What you gain over time is the ability to distinguish between different problem types and then knowing at what stage they need to be addressed.