For PA and dystopian novels, sometimes older is better.
Earth Abides -George Stewart
Alas, Babylon -Pat Frank
The Postman -David Brin
A Canticle for Liebowitz- Walter Miller, Jr.
and for a real challenge, Riddley Walker by Russell Hoban
Space Merchants- Frederick Pohl and CM Kornbluth
1984- George Orwell
The Sheep Look Up - John Brunner
And Russian authors seem to have a great ear for PA/Dystopia. I loved Metro 2033 and Roadside Picnic. Going to watch Tarkovsky's Stalker movie this w/e. It is free to view in 2 parts on youtube. I also hope to read We by Yevgeny Zamyatin soon. It is supposed to be one that greatly influenced Huxley's Brave New World and Orwell's 1984.
check out goodreads.com if you haven't yet. They have a wealth of books and reviews on them. You can search by genre, join a group (check out the Apocalypse Whenever group), etc.