I must be getting old. I checked out this book on google and after reading about the plot I realize that I have actually read this book before, when it first came out. But since I cannot remember who the killer was I will read it again when I get a chance.
Apparently it is story of how Bosch is suspected of taking laws into his own hands. This is not an unrealistic idea. Since this is an anonymous forum, and I am now in a foreign country, I can say that I have personally done same. I personally get very angry when innocent and defenseless women and children and old people get victimized, and sometimes I would do whatever was necessary to make sure that dirtbags were punished and the victims were safe, regardless of rules and regulations etc. This has not caused me one second of guilt, but did lead to a great many career difficulties. That is why I ended up investigating only crimes that occurred in prison, where there are really no "innocent" victims, and it was much easier to remain objective.
My point here is that whenever you read a fictional novel about cops who do extra-judicial things and take the law into their own hands, of which this is a very common theme, do not think it is far-fetched, because it isn't.
It gets a 5 star rating from me.