I'd already gone through it dozens of times, and was reasonably sure that the latest proof would be good enough to approve for printing and selling. It was already a few weeks late -- which is normal.
As soon as Bill, our UPS driver, delivered the box from Lightning Source, my printer, I gave it to Dave. He's my youngest employee and has better vision than I have. He also has good artistic judgment and his mother owned a bookstore. Hawkeyed Dave studied each page, and spotted one line of text that was not indented properly in a paragraph with a "hanging indent."
I quickly decided that I could not let the book reach the public in its present form, and read on.
I ultimately found seven pages that could be improved. Other than the page with the bad word spacing, none of the seven would have been bad enough for me to delay publication by a week, but taken together, I had good reasons not to approve the book.
And... as long as I was fixing up the interior of the book, I asked my artist to make some little fixes on the cover. There were three little bits that had bugged me. I doubt that anyone else would have noticed them. But as long as I was going to delay publication to fix the inside of the book, I may as well use the opportunity to fix the outside, too.
No book is perfect -- not even books produced by the big guys in Manhattan -- but it's important for my books (and all books) to be as close to perfect as possible.
When do you stop checking a book for errors? When you can examine every page and not find anything to fix.
Self-publishers have an extra burden to turn out good work, because each sloppy self-published book reflects badly on the others.
Q: What's worse than biting into an apple and seeing a worm?
A: Biting into an apple and seeing half a worm.