Q: How many proofreaders does it take to make sure your book is error-free?
A: At least one more than you have.
I work for the Marion Zimmer Bradley Literary Works Trust, which has been publishing her backlist since 2005. We started with Fictionwise. Fictionwise, alas, is no longer with us, but its (multi-format) inventory was acquired by Barnes & Noble and converted to Nook eBooks, limiting the format available to ePub. Because the Trustee and I both have Kindles, we took the original source files and published Kindle editions. Recently one of our readers complained about the quality of Falcons of Narabedla, or, more accurately, its lack of quality.
I read the publicly-available version and was appalled. Did we release this, or did it escape? I'm amazed that nobody ever said anything before this. I really hope people don't think we consider something filled with errors as acceptable quality. For the record, we don't. We replaced the files for both the Kindle and Nook versions, and we did a paperback edition while we were at it.
The eBook files for most of our older books are created by purchasing a used copy and having it shipped to the Humanities Computing Lab in North Carolina. They do great work there, so the digital files we get back are in pretty good shape. We do, however, need to check every Darkover book to make certain that the spell-checker has not changed coridom (the Darkovan term for the steward of an estate) to condom, which is in its dictionary. Ditto laran and loran (LOng RAnge Navigation), a problem made worse when MZB named a couple of characters Loran. Sigh. When your source is an old paperback, it is all too easy for "ri" to become "n" and "rn" to become "m" (I had to change comer back to corner in quite a few places), and for commas, semi-colons, and periods to become hopelessly confused. Nowadays we have somebody who has not read the book before (i.e.: not me) proofread it before we put it on sale.
This year the Trust joined Book View Café. Our debut book, The Complete Lythande, is being released on November 5th. Everything but the last story in it has been previously published, some of the stories are available separately, and the book was proofread after we turned it in. Then it went to the formatter, who found still more errors.
I have become convinced that no matter how carefully any number of people proofread a book, there are still going to be errors. A misplaced comma. Dialog in the middle of a paragraph starting without the opening quotation mark. "To" when the word should be "too"; "wondered" instead of "wandered"; "worse" instead of "worst"; etc. (the last three come from a short story published by Baen).
Most readers will not notice a few minor errors because readers get caught up in the story and they see what should be there. So we do the best job of proofreading we can manage and hope that the story is sufficiently absorbing to cover the rest.
Marion often repeated something her father said: "God only made one perfect man, and look what they did to him." I'm not certain whether that's supposed to be comforting or not.