This is the second book in Zahn's Dragonback series. If you haven't read Dragon and Thief, you will be confused, because he doesn't do much to review the unusual relationship between the human protagonist and his very strange alien companion. This is a YA series, and it's a little too blatantly YA in my book. The moral lessons are in-your-face and don't involve a lot of subtle distinctions or hard choices, although I think Zahn may be working toward more nuanced morals as the series progresses. Jack, the teenage boy protagonist, does seem to be growing more principled as the series unfolds. But Zahn descends very nearly to the level of straight lecturing in his by-play between Draycos, the super-moral alien, and Uncle Virge, the strictly look-out-for-yourself AI in Jack's ship. The most painful YA feature is that Zahn appears to find it necessary to completely avoid profanity, no matter how silly it sounds. His characters say "No kidding, Sherlock" more than once, which makes me grind my teeth. On the other hand, I did smile when Jack, in a place where a real person would use an obscenity, swore by "self-buttering Brussels sprouts".
Since this is really a YA book, I have to wonder how a 14 year old would actually respond to it. I'm sure it would depend on the 14 year old; an unsophisticated kid would probably enjoy it, but a more savvy kid might well resent the preachiness.
Other than being excessively YA, the main weakness of this book is that the really interesting stuff -- the nature of Draycos, who does require a fairly healthy suspension of disbelief, but is a truly novel sort of alien, very much in Zahn's tradition of not handing out highly useful abilities without also including very real drawbacks -- all happened in the first book. This book is just space opera with no new SF ideas. Its strength is that it's short, fast, and fun.
In the grand scheme of things, Dragon and Soldier is a weak book, but if you liked Dragon and Thief, you'll probably still enjoy this one. (If you haven't read Dragon and Thief, do read it first.) I was entertained, but I expect better of Zahn. I give it a 6 out of 10.