Over the past decade Dr. Matyszak, who teaches at Madingley Hall, Cambridge University, has written a number of delightfully amusing, very informative, books on the ancient world, such as Ancient Athens on Five Drachmas a Day  (2008) and The Enemies of Rome (2004).

In Legionary, he brings together everything a young man needs to know about military service in the Roman Army in the time of the Emperor Trajan, roughly from the late First Century into the early Second.  Modeled on the handbooks issued to recruits by most modern military services, Legionary covers everything from qualifications for and terms of service, military organization, equipment, discipline, training, and rank structure, pay, life in camp and on campaign, tactics in battle and siege, and more.  It even includes a chapter titled "People Who Will Want to Kill You," which surveys the Empire's enemies and how to fight them.  With it's humorous slant, Legionary catches the flavor of works such as Hi, Hattie, I'm in the Navy Now (1941), which gave young men some notion of what to expect from military life. 

This is not only a very good introduction to military practice in the early empire, but will also be of use to those already familiar with the Roman Army.