Cows, Pigs, Wars, and Witches (Marvin Harris): This was assigned reading in an elective anthropology class I took in freshman year in college. It changed the way I looked at religion and taught me to see people outside Mormon-dominated Utah County's bubble as real people with valid culture.
Foucault's Pendulum (Umberto Eco): Completely spoiled me for conspiracy/occult fiction, and gave me a genuine interest in history that let me see it as, y'know, stuff that actually happened to normal people.
I know there's more, but I can't recall too many specific examples, especially from childhood.