The Unwritten Rules of baseball
I read this back in August of 2010. It is an exhaustive compilation of all those unwritten mores that exist in baseball that on occasion lead to dugouts emptying or "purpose pitches". I found it humorous but filled with the history of these customs that have been passed down from generations to today. Think Zach Greinke and Carlos Quentin or Cole Hamels and Bryce Harper.
This is a must read for baseball fans and those who enjoy the history of the game