You may wish to try the "Roma Sub Rosa" series by Steven Saylor. These books are set at the end of the Roman Republic, and feature a detective called "Gordianus the Finder" who acts as a "leg-man" for the Roman statesman and philosopher, Cicero. The books are truly excellent fictionalisations of many of Cicero's most famous legal cases. Very well worth a read.
Currently proofreading The Poison Belt, by Sir Arthur Conan Doyle.