Steven Saylor's historical mysteries set in ancient Rome and featuring investigator Gordianus the Finder.
I started reading this series a few months back after borrowing the first three from a friend at work and last night I finally finished the last book. I really enjoyed the series but obviously thought some where better than others. Two of the best where "A Murder on the Appian Way" and "Catalina's Riddle" which kept me gripped and guessing right to the very end.
Two honourable mentions are "Venus Throw" which delivered a cracking surprise and "A Mist of Prophesis" which delved into the character of Gordianius him much more than any of the preceeding novels.
One of the great strengths of these books is the characterisation he lends to the supporting cast of famous (and not so famous) historical figures. I have read about Cicero many times but I think forever more it will be Saylors' Cicero I imagine, likewise his Catalina and Clodius. You know the author is doing a good job where you hope a doomed character won't be doomed after all. More so in a historical novel.
Many of the final novels deal with events surround Julius Caesar but I got the distinct impression that both the Character and Author where getting a little tired of late Roman Republic shenanigans. That's not to say I didn't enjoy them (I really did) but it might be time to start wrapping it up.