Recs if you like On Duties (De Officiis)...

This isn't MY list. These are the foundational texts of the Western Canon. Up until the early 1900s, these were unquestionably part of any educated person's background. Austen, Lewis, Twain, James, Sayers, Tolkien....what do you think they grew up reading that informed the genius works they created? Their masterpieces didn't materialize out of thin air. This list is by no means comprehensive, but you'll be off to a solid start.

A compilation of Greek and Roman classics.

Some related lists pinned in the comments

We often talk about what Rizal wrote, but what did the National Hero consume to write so well? To think in that way? Rizal was known to be a voracious reader, getting it from his parents ("[My parents] urged me to read and understand them [books]") and then spending hours in libraries overseas. From his letter to Blumentritt (Nov. 8, 1888): "The Indio, in general, is very fond of reading and studying…”