One of the hundred books a year I read:

The fourth Renée Ballard opens on New Year’s Eve as our Los Angeles detective is paired with an unmotivated sex crimes detective tracking a pair of serial rapists who strike on holidays. They park underneath a bridge, a safe place to avoid falling bullets from revelers discharging their weapons into the air.

Ballard is pulled away from her case with a murder in her district. A hardworking auto repair owner has been shot in the head and killed, though it’s unclear if he is an accidental or intentional victim. A shell casing leaves a key clue—it was fired by the same gun that killed another man years earlier. The detective on that case was none other than retired LAPD detective Harry Bosch.

Dealing with coworkers demoralized by the riots and pandemic, Ballard teams up with Bosch to solve both cases, but the danger ratchets up as they discover a connection between the murderer and the LAPD.