The Silver Pigs by Lindsey DavisRead about the other books on the list.
Roman novels often center on big battles that formed or defined the Empire. The Silver Pigs instead uses the Roman backdrop to set up a mystery, relating to the smuggling of silver ingots, or “pigs.” We are soon introduced to our proto-private detective—a Roman called Falco—who is hired in by the Emperor Vespasian. Of course, there was nothing like a modern police force in Ancient Rome but, just like in modern detective fiction, Falco’s investigations allow him to poke his nose into both low and high society—including forming a relationship with a woman of high birth—and thereby gives us a view of Roman life away from military camps and palaces.
See Lindsey Davis's top ten Roman books and ten top books about ancient Rome, and Tom Holland's five worthy books on ancient Rome.