Excellent series of biographical sketches of the more famous Roman commanders, that also serves as a fine, overall military history of the Republic and much of the Principate, as well. As is typical for Mr. Goldsworthy, there is plenty of analysis, always astute, and his conclusions are always well thought out, and commandingly delivered. 
This book can easily serve as a primer on command, as men, and armies, have changed with their trinkets and toys, but little in their overall nature in the intervaling years, since the days of the Legions of Rome. 
Very highly recommended.