I read this book in 2 sittings, 5 hours total, within a 24-hour window.
But I can't say this is a book you cannot put down. I wanted to put it down many, many times. Because it is unflinching in its portrayal of one view of a post-apocalyptic world (one that I think is closer to the truth of what would happen than similar books I've read). I gave myself little breaks in which I would stare out the window, miserable, until I was ready to soldier on.
That is precisely what the father and son in this book are doing, attempting to get to someplace warmer and hopefully peopled by the "good guys." Walking the interstates and country roads, they are emblematic of the human spirit and soul in its incredible resilience.
And yet there is so much more to the book. The father is of the dead past, and while a good guy he does not have the faith in the present and future that the son has, never having lived in the past. I don't think I've read a book in which the innocence of children is so adequately and completely described. Unfortunately, it makes the story all the more heart wrenching. I recommend it, but I also recommend that you read it as fast as you can.