There was a book I read as a kid, that was set in San Francisco before, during and after the Great Earthquake of 1906 that sparked my interest in history, which resulted in me pursuing that course of study. Unfortunately, I no longer remember the name of the book.
The strongest non-familial influence that shaped me as a person though, wasn't a book. It was a TV show - Star Trek (Original Series). Looking back, I can see how strongly I absorbed the philosophies of that show.