Their coupling isn't unique -- after all, Dashiell Hammett wrote about the married Nick and Nora Charles more than 70 years ago -- but it's still unusual enough to bring a few new angles to the well-thumbed P.
Tellingly, it begins with the image of a sickly, tubercular child, rasping for breath in the night, and then the flare of a light as his older brother reaches for a dime-store paperback, a well-thumbed cowboy yarn he means to read before sleep.