This second outing for married writers Jonathan and Faye Kellerman still feels like a cheap PR stunt, but the results showcase the best story-telling qualities of each. Capital Crimes consists of two novellas revolving around family secrets and featuring cameos by the authors' signature heroes, Lieut. Peter Decker and Dr. Alex Delaware. In ''My Sister's Keeper,'' the investigation into a lesbian congresswoman's murder questions her sexuality, while a burned-out rocker in ''Music City Breakdown'' retraces his misspent youth to a deadly conclusion. Both stories offer satisfying twists and crisp, smart dialogue.