• Roman Blood (1991), in which Gordianus is hired by the great orator and advocate http://en.wikipedia.org/wiki/Cicero - Cicero in 80 BC. This novel is based on Cicero's speech In Defence of Sextus Roscius of Ameria, which is published in the http://en.wikipedia.org/wiki/Penguin_Classics - Penguin Classics edition of Cicero's Murder Trials.
• The House Of The Vestals (1997) (a collection of short stories which appeared later, but which take place between the first book and the second)
• Arms Of Nemesis (1992), about the slave revolt of http://en.wikipedia.org/wiki/Spartacus - Spartacus in 72 BC
• A Gladiator Dies Only Once (2005) (another collection of short stories which appeared later, but which take place between the second book and the third)
• Catilina's Riddle (1993), featuring Cicero and the title character, http://en.wikipedia.org/wiki/Catiline - Catiline , during his rebellion in 63 BC
• The Venus Throw (1995), featuring the poet http://en.wikipedia.org/wiki/Catullus - Catullus , set during the trial of Marcus Caelius in 56 BC
• A Murder On The Appian Way (1996), set just before the http://en.wikipedia.org/wiki/Civil_war - civil war between Caesar and http://en.wikipedia.org/wiki/Pompey - Pompey
• Rubicon (1999), after Caesar crosses the http://en.wikipedia.org/wiki/Rubicon - Rubicon and disperses the Senate, dragging the Roman world into civil war
• Last Seen In Massilia (2000), taking place in Massilia (now http://en.wikipedia.org/wiki/Marseille - Marseille ) during the siege of the city by Caesar's men
• Mist Of Prophecies (2002), set during the Roman civil war in the city of Rome, divided between hopes and fears
• The Judgment Of Caesar (2004), taking place in Egypt, when Caesar met queen http://en.wikipedia.org/wiki/Cleopatra - Cleopatra in 48 BC
• The Triumph of Caesar (2008), set in Rome during Ceasar's triumphal celebrations in 46 BC

I've read down to and including Mist of Propehcies. I see I have some catching up to do. As with all this kind of series, it's good to start at the beginning.

My favourite is Robert Harris, who wrote 2 very exciting novels:

- Imperium, about the life of Cicero as told by his slave tiro

- Pompeii, about the daily lives of 4 romans prior to the erruption of the volcano.

His style is as gripping as a thriller.

The Spanish author Leon Arsenal has also written a couple of books about Romans:

- La Boca del Nilo (The mouth of the Nile, about a military expedition during Nero to the heart of Africa)

- Lanza rotas (broken lances, set in Roman Hispania)