I've recently been reviewing a lot of books, mostly self-published but some from professional publishing houses. All are "newbies," books published within the past year.
Although I was aware of the tendency of self-published books to contain errors--grammatical as well as structural--it's discouraging to see just how rampant are these kinds of flaws.
I'm quite clear, now, that the editing end of book publication is crucially important; good editing literally saves the life of a book. As an author I know that the publication of a flawed book is a huge waste of time, because poor writing distracts from immersion in the story and can make the reader give up on the entire book.
My english-teacher background has developed my sense of grammatical correctness--comma placement, correct word usage, well-written sentences--when all that is in place, a story stands a chance of being read and heard.