"Of #1 New York Times-bestselling author Sue Grafton, NPR's Maureen Corrigan said, "Makes me wish there were more than 26 letters." With only two letters left, Grafton's many devoted readers will share that sentiment. X: The number ten. An unknown quantity. A mistake. A cross. A kiss. X: The shortest entry in Webster's Unabridged. Derived from Greek and Latin and commonly found in science, medicine, and religion. The most graphically dramatic letter....