Bosch is a detective, retired but brought back on a limited contract to work on cold cases. He's had a great deal of success in solving crimes but been far less successful in climbing the career ladder. Being kind, I'd call him a driven loner who lacks empathy. Being unkind, I'd say he was surly and arrogant. Be that as it may, there's a well-crafted book here.
This is a tale of two deaths. One is a cold case, involving a rape/murder. DNA on preserved evidence shows a suspect - but he was eight years old at the time of the murder. The second death is a suicide, apparently. Investigation shows there's more than meets the eye.
Bosch being Bosch, there are personal complications: the second death is that of the son of a powerful local politician - one who hates our hero (the feeling is mutual). There's a brief romantic interlude with the therapist of the rape/murder suspect, there's a daughter at home. There's also the Byzantine politics of the Police Department itself: all get in the way of the driven Bosch.
I said "well-crafted"; perhaps I should have said "solid". This is a competent book but with few surprises. It has the tone of a very good writer producing something to fill a contract. Connelly won't be ashamed of it but neither will he be boasting much about it.
Should you read it? If you're a Bosch fan, yes. If you're new to the character, read a few of the earlier stories first.