I also just noticed that both of these books are published by W. W. Norton & Company. They both have what appears to be the same or very similar CSS style sheet, which is way over formatted for an eBook. Although I see no obvious margin-right properties that would cause the issue.
I looked at the OPF hoping to see which application they used to create the KF8 books, but it only shows calibre. I wonder if this is because I used calibre to explode the book?