“Shut Up!” has become a mall moll’s colloquialism to express disbelief. The watchword cautions a noisy crowd into meditative reception. It is a catchphrase that lessens the loud babbler and empowers the silent observer. In other words, as the book’s title suggests, we should stop our palaver and ponder the quiet person.

Susan Cain executes a fine defense of moderate people in a frenetic world. A former Wall Street attorney, she has presented an academic product as is evidenced by approximately 47 pages of endnotes as well as her 16-page introduction. Citing clinical studies, expert opinions, and professional comments, she traces the history of her subject from individual chivalry and personal character to our current culture of marketable personality.

Her exemplars and case studies substantiate the biological differences as well as some cultural nuances surrounding our understanding of extroverts and introverts. And yet, no person is completely outgoing or entirely introspective. There is balance, and we may have elements of both behavioral traits.

Cain’s compilation of material and weight of argument guides us to nod in agreement that we live in a society that is fixated on outgoing stylists rather than the ponderous sustainers. We live in a world of yin-and-yang; there is no extrovert without an introvert present. Her elucidation might prompt a private understanding of our personality makeup.

A final chapter offers suggestions to parents and teachers about cultivating the introverted child. But Cain’s creation is more a textbook than a self-help guide. Although her style is readable, it tends to be treatise-like and rather dry, lacking the hype, glibness, or glossy banter of a self-help guru akin to John Gray’s Men are from Mars… franchise.

While comprehending this book you might experience some self-awareness—an “aha” moment—that cries out: “I’m not an introvert; I’m merely highly sensitive.” But you’ll not discover that epiphany unless you hush up and read this book.