Tricky one this...
I have read quite a few post-apocalypse books over the years, but they predominantly have a strong science fiction basis; The Day of the Triffids and The Kraken Wakes, both by John Wyndham, for example, or I am Legend, by Richard Matheson (I can also name several post-alien invasion books, but I'm guessing they won't exactly fit the remit either!)
The only one I can think of immediately that doesn't have a strong "fantastical" angle is The Drowned World, by JG Ballard. It's a good book, but not exactly heavy on the laughs...