The Drop by Michael Connelly

Harry Bosch is back, busily raising his daughter by himself, while working in the Unsolved crimes division of LAPD. The unit routinely subjects old evidence to new technology and techniques, like DNA testing, and when a match appears on a blood sample from a thirty year old case, he and his partner, David Chu, get assigned to investigate. The odd thing is that the sex offender whose blood matches would be perfect for the crime, except for the fact that he was only eight years old when it occurred.

Just as they are diggin into the case, Harry gets pulled away to investigate the apparent suicide of George Irving, son of city councilman Irvin Irving, with whom Harry has a history of conflict. It seems that Irving believes he can trust Harry to follow the investigation wherever it might lead, as he has always done in the past, without regard for the consequences.

Though the intitial investigation team has ruled it a suicide, Harry and Chu discover some evidence of a struggle in the hotel room from which George jumped to his death, and begin to pursue the thread of a murder investigation. Young George was a political influence peddler, who traded on his dad's position with the city, charging people a fee to get city contracts approved, zoning requirements waved, etc. Along the way, he has made some enemies, and it seems at first that one of them helped him out the window to the pavement.

In the lulls between events in that investigation, Harry and Chu continue to work on the cold case, which leads them to track down a serial rapist and killer. Harry gets romantically involved with a psychiatrist working with sex offenders, Hannah Stone, along the way, which leavens the professional plot with a bit of the personal, as does his relationship with Maddie, the daughter he is raising after the death of his ex.

The twists and turns of the highly political murder/suicide investigation are pretty good, Harry is his usual stubborn self, and we hope he doesn't retire too soon.