It's an oddly constructed story, but I've enjoyed it all the same. The first half proceeds as the relatively normal life of man and his companions: it's only in the second half that everything falls apart. In some ways it's jarring, because one gets lulled into the every day drama of the first part of his life, before being plunged into the dark last days of mankind. It works well, though, because it means you get attached to the characters before they perish, and appreciate all that the main character lost when the world died. It inflates the hoplessness of the last days, when you can contrast the two (unlike many modern apocalypse narratives, which tend to begin at the end, so the only way is up from the first chapter).