Resurrection Men (Inspector Rebus #13) by Ian Rankin

Inspector John Rebus has messed up badly this time, so badly that he's been sent to a kind of reform school for damaged cops. While there among the last-chancers known as "resurrection men," he joins a covert mission to gain evidence of a drug heist orchestrated by three of his classmates. But the group has been assigned an unsolved murder that may have resulted from Rebus's own mistake.