From wikipedia: The SPQR series is a collection of historical mystery stories by John Maddox Roberts, published between 1990 and 2010, and set in the time of the Roman Republic. SPQR (the original title of the first book, until the sequels came out) is a Latin initialism for Senatus Populusque Romanus ("The Roman Senate and People"), the official name of the Republic.
The stories are told in first-person form by Senator Decius Caecilius Metellus the Younger (born c 90-95 BC), nephew of Metellus Pius and member of the powerful Caecilius Metellus family of the Roman Senate. The stories are told in flashback-form by the old Decius, writing during the reign of Augustus Caesar. The stories range from 70 BC (The King's Gambit) to 20 BC ("The King of Sacrifices"), and have both an exciting and comedic tone.
Decius' companions include his slaves Cato, Cassandra, and Hermes; his friends, the Greek gladiatorial physician Asklepiodes and the gangster/politician Titus Annius Milo; and his staunch enemies, the siblings Clodia and Clodius. Along the way, he is often helped by his father, as well as by Cicero and a young Julius Caesar. In later books, Decius is betrothed and then married to the (fictional) niece of Caesar, Julia Caesaris. The dates are all listed at the end of each book in the ab urbe condita calendar system.
Listed at about 80% of lowest Amazon prices in similar condition. Books included:
II - The Cataline Conspiracy
III - The Sacrilege
V - Saturnalia
VII - The Tribune's Curse
VIII - The River God's Vengeance
XII - Oracle of the Dead