Durant’s Caesar and Christ is excellent. It covers from the Etruscans to Constantine, with significant time spent between the Gracchi and Augustus, in my opinion, the most interesting 150 years in world history.
For a look at the Punic Wars, nothing can beat Polybius. He was a Greek who worked with Scipio Aemilianus, and his writings are in the Penguin Classics series as The Rise of the Roman Empire. It also covers the conquest of Greece during that time period. You also might want to check out Livy’s stuff on the Punic Wars.
Ammianus Marcellinus gives a comprehensive account of Julian’s reign in the 4th century, and Gore Vidal’s Julian is a good fictional account of the same time period.
Other good fiction -
- McCullough’s First Man of Rome series for the revolution
- Robert Graves’s I, Claudius and Claudius the God for the Julio-Claudian dynasty
- Steven Saylor’s Roma Sub Rosa series, detective stories set between Sulla’s dictatorship and the crossing of the Rubicon
Actually written by Romans -
- Tacitus’s Annals and Histories, again, covering the Julio-Claudians. Tacitus is considered to be one of the best historians of all time.
- Suetonius’s Lives of the Twelve Caesars is great gossip
Later historians -
- Gibbon’s Decline and Fall of the Roman Empire, from the death of Marcus Aurelius to the fall of Constantinople. If you care at all about the Byzantine empire, read the last three volumes. If not, they aren’t necessary.
- Macchiavelli’s The Discourses is an analysis of the structure of Roman government under the Republic.
- Theodore Mommsen, a German of the late 19th century, has a good, relatively short (compared to Gibbon) comprehensive history of Rome. Unfortunately, it’s slightly hard to find.