I would only read Irish books when I was younger - James Stephens, Flann O'Brien, Michael McLaverty, the Blasket books. Or else politics, history, philosophy.
I must have lightened up a bit later on, that's when I started reading about murder as entertainment. The classics, of course, Hammett, Chandler, Cain, Himes, Parker, Macdonald, Jim Thompson. Then Ellroy, Mosley, Burke, Rankin, then all the Scandanavians (the Icelander Indridason is the best).
Started to match books to the places I travelled to -Orhan Pamuk in Turkey, Camilleri in Italy, Montalban in Spain, Mercier in Portugal (originally in German).
I started to write Blood from a Shadow as a standard thriller, no big messages. Then I realised I couldn't help it, all that stuff about being an underdog, free will limited by inherited cultural baggage and everyone's basic human right to be treated with dignity, it all had to come out.
Nobody else will notice, but at least it has worked for me. That's all any writer can hope for.