Given his contempt for authority, his tendency to pursue investigative avenues of his own choosing, and his habitually ornery manner, it's a wonder that John Rebus hasn't been booted unceremoniously from his job as an Edinburgh cop. He certainly tempts that fate again in A Question of Blood, which finds him and his younger partner, Detective Sergeant Siobhan Clarke, trying to close the case of a withdrawn ex-soldier named Lee Herdman, who apparently shot three teenage boys at a Scottish private school, leaving two of them dead, before turning the pistol on himself. "There’s no mystery," Siobhan insists at the start of this 14th Rebus novel (following Resurrection Men). "Herdman lost his marbles, that’s all." However, the hard-drinking, chain-smoking Rebus, who'd once sought entry into the same elite regiment in which Herdman served (but ultimately cracked under psychological interrogation), thinks there's more motive than mania behind this classroom slaughter. Perhaps something to do with the gunman's role in a 1995 mission to salvage a downed military helicopter, or with Teri Cotter, a 15-year-old "Goth" who broadcasts her bedroom life over the Internet, yet keeps private her relationship with the haunted Herdman. Rebus's doubts about the murder-suicide theory are deepened with the appearance of two tight-lipped army investigators, and by the peculiar behavior of James Bell, the boy who was only wounded during Herdman's firing spree and whose politician fat