Excellent. A future classic of Space Opera

Simply excellent: a small jewel of Space Op, well-crafted, well built, with a pleasant style that deserves attention (special mention for the translation).
The background of the story is solid, it is often funny, and it has the merit of being concise.
The idea is original and the first part is a marvel. The suite is more classical, note even a slight decrease in rhythm in the second part (succession war paintings), and an end a little too predictable.
The whole is a fairly transparent synthesis tribute to the great classics such as Star Guards to you Heinlein (straship troopers) and The Eternal War by Joe Haldeman. One can hardly do better.
It is the highest level. I recommend this reading warmly.

Note from 27.07.2013: Space Opera is not the favorite genre of John Scalzi, who despises a little this sub genre. This trilogy (the fourth installment of the series being anecdotal) is a commissioned work for an author who was unable to publish his sketches SF - which incidentally have nothing astounding. In the spirit of Scalzi, "the old man and the war" was meant above all a work of parody, in which he integrated into a solid and classic SF plot his penchant for fun. Hence the iconoclastic starting point of the series. But as sometimes happens when a talented author is assigned a control in a defined genre, it turns out in the end that this forced orientation SF "military" yielded the best work done (and best selling) by John Scalzi. All his other books are indeed far less convincing.
Proportionately, Simenon has had exactly the same mishap with his character Maigret, especially as sales of its famous Commissioner were not commensurate with his most personal works.
Unfortunately, if Simenon Maigret continued to write throughout his career, seems to have abandoned Scalzi currently Space Opera "serious". Much to my disappointment.