Did you know that publishers could change their minds about books already accepted for publication? They do have that option, and a poorly edited book can be one cause for contract cancellation. This is why even royalty-published authors generally use at least two kinds of editors before their publisher sees the book manuscript’s first draft.
Developmental Editing: There are several types of editing used for books.  The first one is “developmental editing,” which looks for missing information – or redundant information – and advises writers of these core issues that need to be addressed in a rewrite.  This is a real help for self-published writers, but even for those who have royalty contracts, it’s helpful to fill in missing information or eliminate redundancy before your publisher sees the manuscript.  
Copy Editing/Final Eyes Editing: The more commonly known kind of editing is “Copy Editing” – also known as “Final Eyes Editing.”  For royalty-clients, having a clean manuscript before you send it to a publisher is vital – a sloppy manuscript does not bode well for a publisher’s welcome embrace.  For self-published authors, this is even more important. A poorly-edited book is not just a turn-off, it can lead to negative reviews that can stifle book sales.  For this reason, we have an agreement with a professional book editor who can provide this service, usually but not exclusively within the context of a larger book deal, as noted above and below.