Sgt_Kickaxe - 7:17 am on Jul 18, 2012 (gmt 0)
You've got to analyze the traffic in order to make any sense of the overall condition of a site. Which pages? Traffic Source? Link profile of those pages? Web search or image search? etc.
Your pages may be a book to you but they are a bunch of individual pages to Google, they don't all rise and fall together regardless of what the book does.