Whether self-publishing or submitting to a publisher, you owe it to your work to ensure that it is as good as it can be before you put it out there.
Submitting to a Publisher
Professional editing can do something you cannot do for yourself: see your manuscript through the eyes of an editor.
Acquisition editors are busy people. They always have more manuscripts to review than they have time to review them. Although they are all committed to identifying excellent manuscripts, they often conceive of their job as plowing through the slush pile (that is to say, unsolicited manuscripts; which is to say, your manuscript) as quickly as possible, so that they can devote more time to those few that show the most promise. That means they are looking for any excuse to stop reading your manuscript and so move onto the next.
Don't give them any excuse to stop reading your submission.
Substantive editing (or "structural" editing) can identify the problems of character, plot, setting, pacing, flaws in logic, and so on that are difficult for the originator to recognize, but which will leap out at the acquisition editor and send your manuscript into the "Not for us" pile. Careful copy editing can similarly eliminate minor errors that are next to impossible for you to catch in your own work, but which quickly accumulate in the mind of the acquisition editor into a "No". Even if your manuscript is good enough to keep the editor reading through to the end of the first three chapters (which, along with a synopsis, is all you are usually permitted to submit), the editor won't send for the rest of your manuscript if everything isn't perfect. They get enough polished manuscripts, they don't need to work with even a diamond in the rough.
What many people fail to realize is that successful writing is all about revision. It is human nature to be proud of our first drafts, and to hope that that draft is "good enough". But "good enough" seldom is. A substantive editor can push you to dig deeper, write better, and move past 'good enough' to true 'excellence'.
Even the most promising early drafts have less chance of being published than one that has already been edited and revised. Well, which would you choose in the editor's shoes: a draft that they now have to spend time and energy to edit; or one that has already been edited for them? The problem is, you only get one shot at the editor: once an editor has rejected your manuscript, that's it for that publisher. Make sure your manuscript is as refined and polished as possible before you submit it for publication.
Essential Edits can also review cover letters, manuscript format and synopses to ensure these are to professional standard. The wrong covering letter can put editors off before they even pick up your manuscript; poor formatting screams 'amateur', as does an overlong or imprecise synopsis. In the competition for the few publishing spots available, impression management matters.
Traditional publishers provide a variety of editorial supports; if you are going to take on the role of publisher, it is now up to you to arrange for these services for your authors—even if that's just you.
Almost by definition, authors cannot spot the problems in their own manuscripts, whether these are structural problems at the level of plot, characterization, setting, and so on; awkward or unclear passages; or simple typographical, spelling or grammatical errors. You owe it to your book, to your readers—and most of all to yourself—to provide the same level (or better!) of editing that a traditional publisher would have provided.
A substantive editor can provide several services that every self-published author requires.
Objective Appraisal of Readiness
It is difficult to know when your manuscript is ready for self-publication.
Some writers succumb to the temptation to rush into print while the book is still a preliminary draft. Uncritical praise from friends and family may encourage going with a draft that is 'good enough', rather than waiting until one has achieved the manuscript's fullest potential. Many self-published writers have told me they now regret rushing to publication a manuscript in which they subsequently recognize a multitude of flaws.
Other writers find themselves obsessively polishing their manuscripts, unable to let go, or to take the next logical step. Comparing their current manuscript to those of their favorite published writers, they fear theirs comes up short. What they fail to realize is that it is an unfair comparison: the test is not whether the manuscript stands with the three or four best books they have ever read, but whether it compares favorably to those currently on the bookstore shelf.
Traditional publishing provided a simple test of whether the manuscript was ready: one submitted it to various editors and awaited their decision. In self-publishing this step is absent. A substantive editor can fill this gap, however, by providing an objective and professional appraisal of both the artistic merit and commercial potential of the manuscript. The author is then able to make an informed decision whether to publish now or to revise further.
If a decision is made to continue revising a manuscript, considerable time and effort may be saved by seeking the advice of a substantive editor. Heinlien famously said never to change anything unless an editor demanded the change. It is not uncommon for writers to endlessly fuss over details that do not matter, while missing or avoiding gaping holes in, say, the plot or character development. A substantive editor can help direct an author's efforts to the precise issue that needs to be addressed, and offer suggestions for possible solutions.
Such suggestions do not constitute an appropriation of the author's artistic control. On the contrary, they allow the author to efficiently and effectively regain control over a manuscript that may have gotten away from them. Just as it is easier for an objective editor to identify flaws, it is often easier for someone removed from the writing to see the manuscript's full potential. Dispirited by a manuscript that fails to jell immediately, or that is uneven, or that has some fatal flaw, the author is often tempted to abandon the whole project. Throwing the baby out with the bath water, however, is generally the wrong solution. By suggesting possible avenues the author could explore, the substantive editor is often able to assist authors in connecting the dots when themes are not sufficiently clear, smoothing out rough edges when the writing is uneven, and in the surgical removal of potentially fatal flaws—without killing the patient.
Similarly, a substantive editor can often assist authors in overcoming writer's block, particularly when they are already familiar with the manuscript or project. Writing is at least as much about managing angst as it is about craft. Provided you have chosen the right substantive editor, relevant moral support—appropriately intermixed with the occasional, well-time kick to the seat of one's pants—can mean the difference between successful completion and yet another unfinished manuscript.
Once the decision is made to proceed to publication, it is the publisher's responsibility (that is, your responsibility) to ensure that the manuscript is properly copy edited. Very few authors can do this effectively on their own. It is well established that one sees what one expects to see when reading, and having written the page in the first place, spotting the random errors that are actually there is next to impossible. Friends and family may be able to assist, if you are fortunate enough to have friends and family well versed in the finer points of grammar and composition. If you wish to publish a professional quality product, however, you are likely going to require the services of a professional copy editor.
Consumers are often reluctant to take a chance on an unknown author, or one with whom they are unfamiliar, even from established publishers. This reluctance is greatly increased if they believe the author is self-published, as previous experience may have shown them that self-published works often lack professional standards. Sample chapters posted on the web are a partial solution to increasing buyer confidence, as is professional coverart, book design (layout, font choice, etc.), a convincing-sounding press name, and a professional-looking logo.
None of these will help, however, if the opening page does not immediately engage the consumer's interest; a substantive editor can help ensure that first impressions are positive. Similarly, consumers and reviewers will quickly rebel if quality control is absent: opening the book at random and finding errors a copy editor could have caught quickly reveals the book to be an amateur production. Eliminating issues that undermine buyer confidence is one key to commercial success.
Consumers expect the quality control provided by professional editing. Listing an editor in the colophon therefore increases consumer confidence by suggesting that the book has indeed undergone professional editing. Of course, anyone can make up an editor, so it helps if the editor has an established reputation.
Invest in your writing—invest in professional editing.