The Indispensable booklist

[Gorgon]

My two cents:


On general Roman History:

- A History of the Roman World: 753 to 146 BC (4th edition), H. H. Scullard
- From the Gracchi to Nero: A History of Rome from 133 BC to AD 68 (4th edition), H. H. Scullard
- The Beginning of Rome, Tim Cornell


On the Punic Wars:

- The Punic Wars, Brian Caven
- The Punic Wars, Adrian Goldsworthy
- The First Punic War, J. Lazenby
- Hannibal's War: A Military History of the Second Punic War, J. Lazenby


On Equipment:

- Roman Military Equipment: From the Punic Wars to the Fall of Rome (2nd edition), M.C. Bishop, J.C. Coulston


Others:

- The Creation of the Roman Frontier, Stephen L. Dyson
- The Spartacus War, Barry Strauss
- Caesar, Christian Meier
- Sertorius, Adolf Schulten
- Quintus Sertorius and the Legacy of Sulla, Philip O. Spann
- Quintus Sertorius: Citizen, Soldier, Exile, Philip O Spann
- Exploratio: Military and Political Intelligence in the Roman World from the Second Punic War to the Battle of Adrianople, N. J. E. Austin, N. B. Rankov
- Pompey: the Roman Alexander, Greenhalgh
- Pompey: the Republican Prince, Greenhalgh
- Scipio Africanus : Soldier and Politician, Scullard
- Scipio Aemilianus, A.E. Astin
- Ancient Siege Warfare, Paul Bentley Kern
- The Elephant in the Greek and Roman World, Scullard


Other "must-haves" have already been posted here so I refrained from posting them again.