Can't remember the name of this book

[Max]

Hi, I remember reading this synopsis on Goodreads but can't remember the name of the novel for the life of me. It goes like this: a husband and wife couple goes on a vacation or a retreat to a secluded place, where their marriage falls apart. They return, intending to seperate, but the world has ended (or something) and the wife is the only woman left. That's all I remember. Does anyone please please know the name of this book?

[Richard]

Hmm I don't know but sounds like a Twilight Episode

[Swann]

It sounds like California to me.

[Daniel]

Tried www.Reddit.com/r/tipofmytongue?

They might know.