Mary Beard is nice and easy to read and talks about some pretty interesting stuff.

If you're interested in the Early Empire the Aenied by Virgil is a work from the period that really helped to form the idea of the very early mythological lineage of Rome as well as being an important piece of propaganda for Augustus, the first emperor.

If you go onto a website called Perseus you can look at lots of ancient works for free, a good place to start is by reading some of Plutarch's Lives for historical figures that interest you. (Plutarch was a historian from the Roman period who recounted the lives of earlier Roman and Greek people)

In terms of philosophy like the meditations, there are lots of great things by Cicero (one of my favorite people ever)

Or if you want you can look at greek philosophy, which formed the basis for later Roman philosophy. Plato, Aristotle, Epicurus are all good places to looks, and if you want to go really far back Xenophanes and Heraclitus are some of my faves.

Hope these helped!!