I could certainly see enjoying a book like this but at the same time I don't know how high on the list of priorities I'd put it.
It's one of the reasons I feel that something approximating the 30-60 page soft cover chronicles/campaign setting line wouldn't be amiss. I suppose that financially it just isn't viable in the current market considering they've mostly discontinued it even for Pathfinder in favor of the world guide hardcovers, but I feel that monthly books of reasonable length would expand the setting better than twice a year, maybe, hardcover books that go into significantly more depth but leave wide swaths of the setting untouched.
Which, I suppose that's a preference issue. Would you rather know about more parts of the setting but less about each individual part, or know more detail about a few specific parts.