How good are Harry Turtledove's historical fiction works? He appears to have done a series on sea traders in the Hellenistic era and an I, Claudius style book on Justinian's life.
Some of his work, such as the Hellenic Trader's saga is actually very good. Others, such as The War That Came Early is very bad; if one were to wipe their arse after taking a dump, they would find greater literary merit in the feces-stained toilet paper that in that series.