The Pinnacle by Abir Mukherjee; A Violent Masterpiece by Jordan Harper; Murder on the Red River by Marcie R Rendon; The Devoted by Catherine Cho; The Repentants by Kate FosterThe Pinnacle by Abir Mukherjee (Harvill, £16.99)In the eponymous Mumbai apartment block, the immensely rich and those who serve them exist side…