The writing of this story is beautiful, especially the chapters from Pax's POV. Everytime that little fox asks, "Have you seen my boy?" I wanted to cry. All the same, I was not blown away by the plot. The message of finding yourself and your place in the world was good, but the message about war was too vague and ham-fisted. Also, if you've watched Disney's The Fox and the Hound, then you've basically already seen this story done better. The ending is also quite abrupt. 
 DETAILED THOUGHTS: 
 Releasing captive animals into the wild! Not cool! 
 (I don't consider this a spoiler since it happens within the first couple pages and is discussed in the book synopsis). 
 It makes me incredibly angry that the father's character released a hand-reared fox, who has essentially spent his whole life in captivity, into the wild. There is no way that fox would have a chance at life in real life. So he has essentially abandoned Pax to die, simply because he has become inconvenient? Also, I'm still confused why the father made Peter give up the fox? The only explanation given is "we all must make sacrifices in war time." Does the grandfather not like animals? (view spoiler)[This decision is made even more baffling by the realization that Pax was what brought Peter out of despair after his mother's death and is essentially a therapy pet for his anxiety. We then also find out that the father allowed Peter to leave Pax in what the father knew (and Peter didn't know) would soon become a battlefield. Father of the year award, right here. (hide spoiler)] 
 Violence 
 Holy crap this book is violent. Animals are brutally beaten to death and get limbs blown off with very detailed descriptions of their wounds and bloody, shattered body parts. This is for kids? 
 Vague setting, vague war 
 I'm really confused on the setting, as I see some other reviewers were as well. What country is this? What war is this? It can't be the US, as we have had no landed invasions in modern times (and there are cars, so it most be set in somewhat modern times). Is this some war in the future, that hasn't happened in the real world? 
 I suppose you could argue it's not important, as this is a story about a fox and a boy, but I would argue it is. I want to be able to imagine the setting and understand the background of where these characters live and what they're going through, as the war is an important driver of the plot. If the US has been invaded for the first time in hundreds of years, this would be a big deal to the citizens, but the book treats war as this distant spector. The enemy, whoever they are, have apparently succeeding in invading up to wherever Peter's town is, and I recall no descriptions of Peter's town being near the ocean, making this invasion an even bigger deal. And yet, the humans near Peter (only 300 miles away) seem to still be living perfectly normal lives. The only hint we get is torwards the end, that the war is somehow about water. Huh? Is the water where the enemy comes from all contaminated? If we are in the US, then unless the enemy is Canada or Mexico, they had to come quite a long way to find this water! I have so many questions! Vola mentions offhandedly, in regards to the previous war, that the enemy is a different race, and that one enemy solder had an Arabian Nights, soooo the enemy in that war was middle-eastern? 
 I find the lack of clarification on location/time period to be especially irritating in stories that appear to take place in the real world. In Bambi, it wasn't necessary to establish the overall setting, as the story focused exclusively on animals, and we viewers already understand the dynamic between a hunter and deer. But, this book focuses on humans as well and war is a much more complicated "villain" than a deer hunter. I want to understand the dynamic between the humans of this world and the war, but I cannot because the "war" is just this dark foggy mist in the distance and we are told nothing about it. 
 Another book I read recently did the not-quite-real-world exactly right: The Secret Horses of Briar Hill clearly established that it took place in the UK during WWII, at a tuberculosis sanatorium for children. Despite inserting fantasy elements in the real world, you still have a clear grasp on the setting the characters live in. Tuberculosis was indeed a major issue during WWII, and you know what these characters must be living through with the German bombings. Understanding the bigger picture allows you to more easily focus in and care about this one character's experiences and journey. 
 The ending 
 (view spoiler)[As soon as Pax met the vixen, I figured this would go the way of The Fox and the Hound, and it did. Not all that surprising. It was quite abrupt, however. It certainly could have used an epilogue. I would have liked to know what happened with the war (although given the vagueness of it, I didn't really expect much in the way of closure on that front). I also would have liked to know what Peter did afterwards. I thought it would've been fitting for him to go and live with Vola. Or at the very least, can the author tell us how he gets out of the war zone? For that matter, was leaving Pax in a war zone again really a good idea? (hide spoiler)] 
 Minor Issues 
 (view spoiler)[I suppose I can't expect much of a 12 year old runaway, but why would you not just take the whole atlas? How did he think a few crackers and cheese sticks would be enough food for over a week? 
 I also find the premise of Peter's story, that he's going to weight lift enough in 1-2 weeks to be able to hop 200-300 miles on crutches, pretty hard to believe. In the end he only has to go 40ish miles at least, which is slightly more believable, but still pretty hard. 
 How on earth does one bus driver's route cover 250 miles? That is 4.5hrs of solid driving one way at 55 mph, assuming it's mostly country roads. And that doesn't even take into account the stops, cause it's a bus right? It has stops. Does he just not come home everyday? (hide spoiler)]