The main concept that comes through pretty strongly is that the consequences of unbridled human greed, cruelty and evil are devastating and severe. Throughout the book McCormac has the father refer to "the light" that only he and his son carry, to the fact that all of the "godspoke men" are gone from the world. This indicates that god and any sense of morality or decency have completely disappeared from their world. The light that he and his son hold is the light of civility, humanity, kindness, godliness and decency. In a world where all of those traits are gone, it is dreary and awful, and barely worth surviving in at all.
Even the landscape itself reflects the lack of hope and joy in this world; it is constantly cold, raining, gray, and shrouded in the burnt remnants of what civilization used to be. The physical and emotional/spiritual landscapes are the same: devoid of anything that is pleasant, human, livable or comfortable.
As one reads the book, it is hard not to get the feeling that we must not let a world like this come to be; we must keep the light of human kindness and morality alive in the majority of the people around us, including our own hearts, and that will hopefully keep the world a place where joy and happiness can thrive.
I hope that those thoughts help; good luck!
The starkest impression that I got from this book is how the father illustrates the new world order, which has resulted from the devastation that has occurred due to the advances in technology, shared by many in the world, which results in nuclear annihilation of most of humanity.
The author notes that the father and son have been slingshotted to the past, a period of pre-history where survival dominates their entire existence. There are remnants of the past lingering in the new world order, reminders, like ghosts of what civilization had become, there are good memories that the father can access, but most of memories are tinged with serious sadness when he remembers his wife and the buildup to the nuclear war that destroys almost everything.
The author, for me, writing this stark dystopian novel, poses a thought process or philosophy that offers the reader an opportunity to consider whether scientific advances or technology will lead to our ultimate destruction. Modern warfare, now dominated by nuclear missiles and highly potent weapons of destruction if unleashed, as they are in The Road, will lead us to the barren wasteland, back to the past, before man had modern conveniences and a stable life. The father and son are hunter gatherers, like our ancient ancestors who had to scour their environment constantly looking for food which precluded them from creating stable societies.
McCormack tells us that this is what awaits us, a blast of destruction and we, those who survive, lucky or not, that is up to you, are going to have to start civilization all over again.