Bourbon & Blood (Bill Conlin) by Garrard Hayes

This isn't a PI story, even not in the unofficial sense, really. It's more of an action / crime story and would make a pretty good action flick.

Ex-war hero Bill Conlin returns from the war to live in New York. His cousin Jimmy asks him to join the mob and after some refusals ends up doing their bidding. He saves some sex-slaves, kills some gangsters and is set up in a fancy appartment, complete with loads of guns and a good-looking woman. Stuff gets more dangerous, bloody and violent by the second and Bill is soon hip-deep in blood.

There's a lot of tough guy conversations and a lot of violent encounters in this book. There's also a lot of bourbon being drunk. So yeah, the title sums up the story pretty well.

If you think there's not enough action in a Lee Child novel and an Andrew Vachss novel isn't dark enough this one might be for you. Personally, I like a little bit more mystery in a crime novel and a little less action.