Spradlin's book is especially effective because it takes into account what younger readers want, which is action, adventure, and violence, with what the adults handing them the books want, which is a certain depiction that war is not a great option. Henry's enlistment is done out of desperation over his situation at home, which was not unusual at the time. While the story doesn't glorify war, it does celebrate the men who banded together to help each other survive, and showed the triumph of human will under impossible circumstances. The other thing that young readers like is anyone undermining authority, and the prisoners certainly managed to get the better of their captors on many occasions. I imagine that Hogan's Heroes was wildly popular with 12 year old boys when it was on television, for just this reason.
The historical details are rich and interesting; it had never occurred to me that the guards at the prisons camp were the less successful soliders, but it makes sense. The heat and humidity of the jungle, the food rations or lack thereof, and the historical background are all effectively portrayed, and will hold up to the scrutiny of the most well informed war buff.