As a publisher, the bookstore is actually your customer. And of course you want to give your customer good service.
Customers respond well when they are treated well. They buy more of your product. So it's very much in your interest to treat booksellers the way they want to be treated, even if it means a little extra work and thought; bookstores are the portal to your readers.
Some general rules of thumb:
A developmental editor helps you shape your book. Rather than focusing on a line-by-line edit (though some developmental editors also do this), the goal is to focus on the structural organization of the book – does the narrative flow coherently? Are there plot holes? Are terms explained appropriately for the audience?
A developmental editor will help you trim areas of your book that are too long, and punch up details that need highlighting. They are sometimes called “book doctors”.
But do you really need a developmental editor?
Most books need another set of eyes to objectively review the content. It’s a rare author who can write a perfect book without feedback. A developmental editor doesn’t re-write the book, but helps its evolution, in the writer’s own voice.
No publisher has an unlimited budget, and that is also true of self-publishers. Determining the format of your publication affects the overall cost of publishing, so it’s important to minimize your risk.
Ebooks and print books have different costs associated with them. While ebooks are cheaper to distribute because there are no physical shipments, professional-looking ebooks require additional investments that print books might not: in special formatting, adding multi-media (and clearing the rights for them), proofreading specifically for the digital product.
Most of us, even English majors, make grammatical mistakes. The difference between a copy-edited book and one that has not been copy-edited is enormous. Copy-editing doesn’t change the substance of what you’re writing about. In fact, it enhances it – clarifying meaning, correcting distracting mistakes.
A good copy editor will adjust your punctuation and spelling, question whether or not you really want to use jargon, make sure you’re using the right terminology, and keep you from embarrassing errors of usage. He will keep your language consistent from page to page, and ensure that you capitalize names properly.
The ISBN was invented in the 1960s, when British bookseller W. H. Smith began computerizing its distribution system. It became an ISO standard in 1970, and now the ISBN forms the backbone of the book supply chain around the world. Certainly there are plenty of books published that do not have ISBNs. Proprietary publications that are not traded, for example, don’t require ISBNs. Books that are sold in “walled garden” environments don’t require ISBNs. So why use them?