Since the inception of the Amazon Prime Membership program, where members pay into a monthly membership and can download ebooks for free, a new marketing venue to get your books out has opened up.
Post Apocalyptic fiction has definitely enjoyed a resurgence with the popularity of The Hunger Games and Divergent and a slew of other trilogies of the same or similar genre, but even with its renewed popularity, PA fiction is still a niche genre under the Science Fiction umbrella and getting the word out to the general public is still a chore.
But with the introduction of the new Amazon Prime Membership, authors of the dark arts have a new angle, a free angle that will offer more exposure if they decide to include their books into the KDP Select program. This is where Prime Members get their fix of freebies.
So mention your books to Prime members via the Amazon forums dedicated to them and get noticed!