Seriously, this is the book that I am recommending to everyone this year. If you don't check out any of the other books I review, please give this one a try--for an introvert, it's liberating and fascinating; for an extrovert, I can almost guarantee it will be helpful. (My mom has 3 introvert kids and an introvert husband, and she finally really gets what makes us tick!)
There are four sections: 1) the history of the extrovert ideal in Western culture, 2) the link between biology and temperament, with supporting studies as well as ones that might imply less of a correlation, 3) a comparison of cultural ideas about temperament, and 4) practical notes on living well as an introvert or as the parent/spouse of an introvert.
The first section was the most fascinating to me: Cain explores how Western culture moved from respect for thinkers, poets, and "men of character" to celebrity culture, extrovert image, and the ability to be outgoing and work in groups. I wish section three had been longer, in fact; the comparison between current Western culture and other cultures both helped Cain's premise and showcased different manners of social behavior without over- or devaluing any of them.
Equally good were interviews with introverted business people, students, and clergy, and a gorgeous roundup of psychological and neurological studies from the past few decades that indicate some of the roots of personality types.
If you're one of the quiet ones, find out more about yourself and how to contribute to our extroverted culture; if you're not, find out how to benefit from those who are.