First Book Theme

I think the theme within my book is to never give up hope. A man and his son (they aren't given names) are traveling from somewhere that seems to be pretty far north, as they're in snow-covered mountains. Their objective is to travel to the south somewhere, but I'm not sure specifically. I don't believe it's ever listed in the book. While they move through the mountains, they are battling hunger, sleep deprivation, and the always relentless cold. There seems to be no real end to the misery and loneliness of the road. The only people they ever encounter are the "bad guys", that want nothing more than to kill the man and his son. A magnum, with only 2 bullets total to use; he must use them wisely. Through all of this anguish, neither one ever give up hope, even though at times you would think "there's no way I'd make it through that". That is one of the main reasons I like this book, because it has a great descriptive story line, and the characters are genuinely good people with a set objective, as opposed to a story that has no focus on a certain point.