Story now has Bosch retired from LAPD. His mentor has died and left him a mystery - an old murder (blue) book. Being Harry he couldn't resist. He's barely into the cold case when he realizes, he doesn't know why the case meant anything to his mentor. He teams up a with a former partner, Det. Renee Ballard to work it. Ballard agrees to help after her shift. Then she gets two cases to work. She juggled all 3 cases. The story takes Bosch almost to his death and Ballard to hers.
There's familiar language and locations but the story lines are pretty basic. There are no real twists or surprises. It was still enjoyable to listen to.