A newly-published book, Popular Crime: Reflections on the Celebration of Violence, by author Bill James, examines America's ongoing obsession with the crime of murder. It focuses on numerous high-profile and sensationalized instances of murder throughout America's history. The book sounds like a more informal version of The Cases That Haunt Us, but limited to American crime.
Not surprisingly, Bill James apparently devotes some of his attention to the case of the Zodiac. Perhaps someone who has read the book would be kind enough to describe the content as it relates to the case.
Some details of the book, including an excerpt, can be found on simonandschuster.com and The Washington Post has a complete review.