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. Notoriously tricky to pronounce: think xylophone.X: The twenty-fourth letter in the English alphabet.Sue Grafton's X: Perhaps her darkest and most chilling novel, it features a remorseless serial killer who leaves no trace of his crimes. Once again breaking the rules and establishing new paths, Grafton wastes little time identifying this sociopath.