This... The Road by Cormac McCarthy portrays a gruesomely realistic scenario of what one can really expect in a situation where everything modern society takes for granted is severely crippled. Many have speculated just what really caused the widespread catastrophe in The Road, and I have ventured many times to say that it may have been a low level gamma ray burst. A star going supernova between 20-80 light years away with their polar axis somehow pointed right at us, ejecting a stream of high energy particles that are considerably weakened by the distance traveled, but still packing enough power to cause atmospheric ionization and global EMP as the initial outcome. 80-90% of the rays from the jet gets blocked by the atmosphere during the ensuing EMP but the 10-20% of the particles that got through would be enough to wreak havoc on all plant life and kill off vast quantities of plankton and algae that aquatic life depends on for sustenance, and leave the larger lifeforms, including humans, facing starvation. In a situation like this, the unprepared hordes from the cities who are desperately fleeing outward to try to live off of game and fish would VERY QUICKLY find that game populations in the country would be heavily defended by local residents with extreme prejudice, and rightfully so. The scarcity of other human survivors in the novel is easily explained by the fact that those who did not starve to death or succumbed to disease would try to pilfer game animals and resources of local residents in the rural areas they passed, and many would be cut down as bandits.
ETA: Recovery of society after such an event, even with a significant enough population of survivors, would be very difficult, as items like crop seed stocks can very well be damaged. Seed embryos are extremely fragile and unless the seeds were stored in a hardened vestibule, the ionizing radiation from the pulse could have rendered all of them unable to grow, thus, even if the survivors were to have tried sowing new crops after the mass die off from the pulse had been cleared, they may have found that all of their seeds had been irradiated as well and useless. It is one of the most dreadful situations that could be possibly laid out onto paper.