Have you ever read a book older than you are? It can be an interesting experience because so much has changed about societal norms (and publishing trends) in just the last few decades.
One way to give it a try is to revisit the lists of awards I gave you last week and look up the past winners.
You can also Google "award-winning books of XXXX" (year of your choice) and see what happens.
Pick up a classic - one of those books everybody's heard of and supposedly has already read (wait, that's another inspiration prompt we'll get to later). Most of those would be from before your time.
You know how I said societal norms have changed? Often the reason books get "banned" or suggested for review is dated terminology or no longer approved behavior. Take a look at the American Library Association's list of frequently challenged books and find inspiration there.
One last idea: ask an older adult for a recommendation. See what your dad's favorite book was before you were born. Or ask your grandparents about something they loved in the past. It might also start a conversation that takes you deeper in your understanding of them!