How can you confuse nineteen-year-old boy with forty-year-old man? Did he look that bad? Okay, I can believe that uniform can add some years, but not twenty!!! And it is not like Meg saw him only in the dark or from afar. He didn't have a beard and moustache that could confused her. I can understand taking older man for the young one (take for example Shia LaBeouf. It's like he will stay in his sweet sixteen forever), but not the other way around. 
 And I must admit that I want this relationship to happen more when I was sure John was in his forties (that is a little bit disturbing tendencies I found in me :))) 
 All in all, it was very nice short summer read about two horny teenagers with problems.