I read a novel when I was 12 or 13 (late 80's, early 90's) about two timelines combining on Earth. It was a full length novel for adults that I swiped from my mom (she doesn't remember it at all.) I've been trying to figure out what the title is for some time but my google-fu is unable to find the right search terms.
The book was published in the 80's or perhaps early 90's.
The story: It was set on Earth and featured two timelines running concurrently (in the 80's?)
Timeline 1: The nuclear missile crisis had gone badly and a low level nuclear war had more or less destroyed the US, but small towns still survived but are slowly fading away. Much of the story was about the scarcity of goods, and the protagonist in the main thread of the book started the story by finding a 6 pack of Coke buried in a ruined house. Throughout the story people were finding things that had grown scarce (deer, bullets, human beings.) One strange scene I recall involved mutant/radioactive sweet potatoes that had driven a man insane.
Eventually people in this timeline began having dreams of their lives in Timeline 2. Some of the people were not having dreams, and it was eventually discovered that they had died in Timeline 2.
Timeline 2: There is panic in a world recognizable as our 1980's as nuclear war draws near. Since more and stronger missiles have been developed, the end of humanity is at hand. Things start disappearing from that world as the war begins. Timeline 2 was mostly seen as vignettes of panicked people running around.
Combination of Timelines: In a weird, incongruous, almost surely poorly written scene, Gaia (yes, Earth itself) is seen to be combining a dying timeline with a doomed timeline in order to save humanity. At the end of the novel, kids from Timeline 2 are transported into Timeline 1 in order to repopulate. The new kids drink all the Coke, in case you were wondering...
Any help finding the title would be welcome. I recall enjoying the book a lot when I was a kid, but I suspect my mom traded it in at our local used book store because at some point it just disappeared.