Occasionally an author will see a listing for her book on a website she's had no previous contact with. Of course, the immediate question is, "Why are they selling my book? I never engaged with them to do so."
Chances are, they're not really selling it. When an author registers an ISBN with Bowker, that information goes into Bowker's Books in Print database. Many booksellers license BIP, and list the entire contents of it on their websites. They probably haven't made vendor agreements with many of the publishers in Books in Print. They're not stocking the books in their warehouses. If they receive enough orders for the book, they'll track down the publisher and arrange a vendor agreement.
If you’re writing nonfiction, you may want to invest in the services of a fact-checker. Fact-checkers adhere to a rigorous standard, questioning assertions and asking for documentation and citations to support those assertions.
The self-publishing service Lulu has some good tips on fact-checking here. Probably the greatest portrayal of a fact-checking department was written by John McPhee about The New Yorker.
Magazines employ fact-checkers because their publication cycles are not as severe as newspapers, and magazine articles are shorter than book-length manuscripts and therefore not insurmountable for a staffer to fact-check.
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.