The Roman Army is a wonderful little book. I say little because it is only about 48 pages, but those pages are packed full of information, and colorful illustrations.
Wilkes provides accurate details and gives enough information on training, legion formations, legionnaire duties, construction of the camps, and the legionnaire's weapons to equip someone new to this area of study. If you are well-versed in the Roman armies of the times, this might serve as a good refresher, but it is perhaps best used by a younger reader who is new to the area of study. That is where I found it most valuable, as my younger son, who was thirteen at the time, showed interest in Roman history. It was both easy reading and informative.
The period covered spreads a few centuries but deals mostly with the empire during the reigns of Hadrian and Trajan, a bright time for the empire, and a good time to be in the legion.
I will state it again—this book is not for a person well-versed in the history of the Roman Army. This book is better suited to someone new to the field, or a younger student of Roman military history. This book shines in its simplicity and brevity.