The mystery field is broad enough to accommodate writers from Mr. Brown, who can hinge a plot on the difference between matter and antimatter, to Robert Crais ("The Last Detective"), who cranks out the printed equivalent of formulaic Hollywood thrillers. It can feature stand-alone protagonists or serial detectives as familiar as old friends. "As I walked through the room, the men stared at me," observes Robert B. Parker's Spenser in "Back Story," the 30th book in Mr. Parker's unflaggingly congenial Boston-based series. "Probably sick with envy."