@Chuck Finley, looks like this book may be the start of the spin-off series - https://en.wikipedia.org/wiki/The_Wrong_Side_of_Goodbye - "This novel finds semi-retired Harry Bosch alternating between two investigations. As a private detective he is summoned by billionaire industrialist Whitney Vance. The elderly, never-married Vance wants Bosch to track down an old girlfriend to know if he has an heir to whom he can leave his fortune. As a volunteer part-time officer for San Fernando, Bosch is involved in the search for a serial rapist."
there's a series on amazon about "leo waterman" a private eye, kind of a fuck up. His dad wasn't really a mobster per se but ran the city and was corrupt. He befriends a lot of drunks and bums some of whom used to be lackey's for his dad and uses and pays them to assist with investigations. It's a softer more comedic tone at times, but still good. One book in particular sees a homeless guy wind up in the hospital and his friends bust him out, hospital bed and all, and all jump on it and coast down the hills of seattle away from the fuzz and hospital employees.