It is so easy to jump on the internet before, during (!) and after a movie to get quick answers to the questions that come to mind. What was that last movie I saw that actor in? Who was the bouncer -- he looked so familiar? How old is Viggo Mortensen? These are the easy questions where IMDB is your go-to source.
Green Book inspired some deeper questions as the best movies and books do.
General google searching will answer your most likely question, "Is the story true?" I was most curious about the Green Book itself, and the origin of the term Jim Crow.