What Book That You Have NOT Read Has Most Influenced and Shaped Your Life?

This is a fascinating question tweeted by Venkatesh Rao which I encountered through economist and polymath Tyler Cowen.
The question flips over the classic "What book have you read that has most influenced your life?" into a different realm. What text as more subtly influenced you simply by being present in your society? Cowen responds:

I suppose if you haven’t read the bible or quran those are easy answers, but let’s say you have.
I’ve only read snippets of Mein Kampf, so that has to stand as a contender.  But has the book really influenced and shaped my life?  Maybe you can attribute the relevant marginal product to the life of Hitler, with the book being intermediated by Hitler himself.  Therefore I am not sure that answer is true to the spirit of the question.
How about a training manual of some kind, which perhaps my early teachers read but I have never seen or even heard of?  Might my mother have read Dr. Spock or other parenting books?  That would be my best guess.

Benjamin Spock's Baby and Child Care greatly altered (or reflected a developing trend) in American parenting. Many adults would have been necessarily influenced by it, so that's a pretty good pick. Cowen's normally very intelligent commenters also have great suggestions, including Isaac Newton's Principles of Natural Philosophy and the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders.