Resurrection Men by Ian Rankin

Second Hand 

Rebus is off the case. A few days into a murder inquiry following the brutal death of an Edinburgh art dealer, Rebus blows up at DCS Gill Templer. He is sent to the Scottish Police College for 'retraining'. In other words, he's in the Last Chance Saloon.

Rebus is given an old, unsolved case to work on, in order to teach him and others the merits of teamwork. But there are those in the team who have their own secrets - and they'll stop at nothing to protect them.

As if this wasn't enough, Rebus is asked to act as a go-between for gangster 'Big Ger' Cafferty. And as newly promoted DS Siobhan Clarke works the case of the murdered art dealer, she is brought closer to Cafferty than she could ever have anticipated . . .