Midnight and Blue (also Midnight & Blue) is the 25th novel in the Inspector Rebus series by Scottish author Ian Rankin. It also exists as an audiobook, narrated by James MacPherson.
Plot.
The novel carries on directly from "A Heart Full of Headstones", which culminated in Rebus' conviction for the attempted murder of his old nemesis, Big Ger Cafferty. Now, Rebus himself is behind bars. Two parallel investigations follow: one set in Saughton Prison (HMP Edinburgh), in which a prisoner is found murdered in a locked cell, a case which is taken over by Christine Esson, with Rebus as a possible suspect. The second follows DI Siobhan Clarke, as her investigation into the disappearance of a schoolgirl leads her into a world of 'online pornography, pseudo-celebrities and exploitation.' Meanwhile, Edinburgh's underworld struggles to fill the vacuum left by the death of Ger Cafferty, and we see the return of DCI Malcolm Fox, first introduced in "The Complaints", as well as a number of other returning characters, including the psychopathic drug lord Darryl Christie, who seems to offer unlikely support for Rebus in his new environment. 
Themes.
Like "A Heart Full of Headstones", "Midnight & Blue" deals with the themes of the past, the grey areas between good and evil, past mistakes and taking responsibility for them, as well as those of ageing and mortality. Ian Rankin has described Rebus, ageing alongside him in real time, as a kind of proxy, saying: 'He takes on all the aches and pains... that are waiting around the corner for me. I give all that stuff to him so I don’t have to worry about it so much.'
Reception.
The novel was enthusiastically received, with "Kirkus Reviews" praising the 'vividly detailed portrait of the labyrinthine corridors of power in the prison,' and "The Guardian" calling it 'An expertly plotted... addition to a standout series.'