Excellent "boots on the ground" military Sci-fy. 
 Some time in the future humanity has finally made first contact and low and behold they're friendly, non-violent and quite eager for humanity to join their confederation. The catch... they're at war and the confederation members don't kill. So humanity does in their stead, as soldiers/ protectors, killing the elusive enemy the "Others" 
 Half a century later enter no-nonsense Staff Sergeant Torin Kerr is in charge of her Confederation marines. A mixed alien marine force of several younger (read violent) species. She and her battle hardened soldiers are send on a "easy diplomatic mission" to impress a new species in joining the confederations and swell the ranks of the marines with their soldiers. Things go as well as can be expected, ... until they don't and bullets start flying. 
 An interesting world and interesting characters you care for. Kerr is intelligent and competent and a likeable main character. Things don't always go as she wants, but she deals with it. The action is thrilling, the banter great and the cultures and people in them distinct and alive. Add to that a fine sprinkling of humor and wit and you've got one excellent series opener.