The violence quotient varies greatly. Mr. Patterson and Jeffery Deaver get much of their mileage by exploiting tastes for the grisly. "He straightened up, considering what he might do to the still form in front of him," Mr. Deaver writes at the start of his latest Lincoln Rhyme book, "The Vanished Man," describing a homicidal sadist and his first female victim. This is a far cry from Daniel Silva, whose best-selling "Confessor" features the elite art restorer Gabriel Allon as its protagonist. Like Mr. Brown, Mr. Silva deals in characters who know art, roam Europe and might just say something in Latin.