The Prison Guard's Son (Finn Harding) by Trace Conger

Unlicensed PI Finn Harding is back in his third novel. He is hired by the father of a kid who was brutally murdered by two other kids years ago. The father wants Harding to track down the two killers who, after a short stay in a juvenile detention facility went into a WITSEC program and as such very hard to find. He promises Harding he will make sure justice will be done when he knows their locations.
What follows is a fascinating journey into databases, PI tricks and some very creative investigating. It's just amazing how Trace describes this, he'd be one hell of a PI himself.
Of course, there's some brutal action as well, this is not a police procedural but a PI novel.
I enjoyed the earlier novels in this series but I liked this one the best because the writing is much tighter. There's just a better rhythm to it, less padding and better pacing. I just couldn't put it down.