Well, I had an experience most writers don't - the chance to discuss my book with a number of excellent editors prior to selecting a publisher. One of the questions I asked was, "Can you show me some books you did that are comparable to mine, and what you did with them?"
Being Aspergian, and analytic, I took all 50 of those books home and read them to see what the editors meant.
In some cases, the subject matter was similar. I looked at how the other authors described things and was struck by our similarities or differences.
In other cases, the writer was said to have similar voice or tone and I read the book carefully to get a feel for voice.
In other cases, the book was said to do for xxx what my book "will do for Asperger's." I read carefully to understand that.
And finally, I was given one fictionalized account of Asperger's that outsold almost all the non-fiction works. I studied it and the NF works to learn why.
I learned a great deal by hearing how editors categorized my story, and then studing the "similar" stories. For it would never have occurred to me to make most of those comparisons myself.
That was very educational.
Then, having selected an editor, I looked at other books she had done. Was there a similarity in how they sounded? Could I identify the same editor's touch in all of them?
The answer is, yes, you can see it if you look. At least I did. If you have something to compare to. But it wasn't what I expected.
I also found that you can take the big books from the front of a publisher's catalog (as a group) and compare them to the 1/4 page books at the back (as a group) or even books that were produced inexpensively as paperbacks. You will find the 2-pagers are just done better. Sentences read better; things don't come to a jarring halt very often. Errors of readability and sequence and even fact occur less often.
How did I learn that? Well, it was simple. The publishers gave me catalogs, and I reasonably enough concluded that the feature books in front were those the publisher put the most care into. Without a catalog, I'd have had no way to know which titles those were, or which were on the 1/4 pages in back.
I believe much of that difference is quality editing as opposed to different authors. That belief is borne out by my experience moving through the editing process myself. By that, I don't want to suggest that Joe Schmo at the corner is the next John Grisham, just waiting for a good editor. I am merely pointing out that a good editor makes a bigger contribution to the final work than I usually see credited in places like this.
I have now learned how much work it is, doing a quality edit like this. With 200,000 titles appearing in print every year, I understand how there are not enough editors to go around, devoting this level of care to a book. I'm very thankful my own work merited that, in the publisher's opinion. Otherwise, I would never have known.
I don't know how much help my post will be, because much of the appeal of my work is that I don't think like other people. So perhaps my non-standard thinking won't be transferrable; I don't know.
When I am done with editing and have a bit of time I will try and write a story of "what the editor did" in the case of my book in hopes that other writers can apply some of her techniques on their own, to improve the quality of their work.
I will certainly take much of what I have learned to heart as I write my next book.