A comet strikes the Earth, causing enough damage and disruption that civilization collapses overnight worldwide. The novel follows the struggles of various people to survive.
The luckiest ones are those who either live in the same reasonably isolated valley as U.S. Senator Arthur Jellison or who are able to get there and persuade him to let them stay. Among the latter are TV producer/director Harvey Randall and wealthy amateur astronomer Timothy Hamner, co-discover of the comet. Jellison is smart enough and tough enough to organize his friends and neighbors for self-protection and survival. A few others are able to do the same, though with less success. The vast majority, however, simply starve to death or kill each other for the rapidly dwindling available food and resources.
Others find a different solution, forming a cannibal band that has to keep moving to feed itself. When the cannibals head toward the valley, a war erupts.
Best part of story, including ending:
It's a very plausible and equally scary depiction of the end of the world as we know it.
Best scene in story:
Anything involving oddball mailman Harry, particularly when he first encounters the senator's roadblock. It's humorous (considering the circumstances).
Opinion about the main character:
It's more of an ensemble novel, but the closest to a main character is probably Harvey Randall. As written, his actions are pretty realistic.