Bret Devereaux

Alright, let's do this! My first recommendation for someone looking to start reading on this topic is always J.E. Lendon, Soldiers and Ghosts (2006), which offers an basis for the whole business, especially the values that support it.https://twitter.com/mizroba/status/1357446096969216005 …

The next solid 'starting point' book I think is still P. Connolly, Greece and Rome at War (1981), which despite being a bit long in the tooth is an excellent mix of tactics, operations, equipment, individual battles and so on.

More niche topics as you develop that basic knowledge... On the development of the legion, L. Keppie, The Making of the Roman Army (1984) is still a good standard text for the basics of the transitions from the military system of the Middle Republic to that of the early empire.

On equipment, Bishop and Coulston, Roman Military Equipment (2006) is the peerless reference, strongly rooted in the archaeology, for all of your sword, shield and armor needs.

For those with more languages, honorable mentions in the equipment category for Feugère, Les Armes des Romains (1993) and for the reenactor crowd esp., Junkelmann, Die Legionen des Augustus: Der römische Soldat im archäologischen Experiment (1986)