The Disposables (Bruno Johnson) by David Putnam

There's an original twist here... The main character is not a PI although he is certainly a tough guy. In fact, he's
part criminal, part hero. Ex-cop Bruno Johnson has set up an underground railway-system for abused / neglected kids together with his girlfriend and his dad. To finance this he sometimes does jobs for a criminal.
When a cop he used to work with bullies him into going after a high-profile pyromaniac / killer his life becomes even more complicated.
The writing style reminded me a bit of Walter Mosley at times, especially his newer series work.
The author has been involved with law enforcement most of his life what gives this book an extra realistic edge. I hope most of the people Mr. Putnam had to work with were a bit nicer than the cops introduced here, though.
While the plot might have been a bit tighter or more logical at times the realism and original subject matter still makes this book a winner.