There's an interesting and readable series of mysteries set in ancient Rome. The series is called SQPR (I through XIII) and named subtitles. The first is SPQR I: The King's Gambit.
It follows the efforts of a poor but honest, minor Roman official who tries to solve a murder that took place in the part of Rome he was responsible for. Not everyone wants the murder solved. We see the interplay of politics and factionalism against daily life in the First Century BC.