I've said goodness knows how often that the biggest mistake any independent author can make is to think that they don't need the services of a professional editor. Granted, errors are not unknown in professionally-published books, but they are far, far, rarer than in the typical indie book. Some indie authors do it right, of course, but they are the exception.
EDIT: You're saying that this WAS edited?
In that case, the author should get themselves an editor who knows how to do the job properly!