Option pages
Pro
An option page is a settings screen in wp-admin whose values apply to the whole site, not to one post: the business's opening hours, a support phone number, the footer text, a promo banner that runs site-wide. There's one set of values per page, shared by the whole site.
You build the page under VX → Option Pages, and design its form with a fieldset that has an Option Page Location. Then editors fill it in like any settings screen.
Values that belong to each Book or Writer don't go here; put those on the post type.